Please forgive me for this very long reply. Your initial posting really struck a chord in me and I felt the need to offer my experience for you to consider.
It is hard to add much additional advice to that already offered. The posts by Amanda (aaajjj55) and SadieBlake really get to the central issues, IMHO. You chose well to come here for advice--that is why I chose to add a reply to this thread--the advice I received here has helped me to get through some very difficult times. I hope my experience will give you some insight into the problems your husband may be facing and how it feels to be him. It has taken the better part of 6 decades but I am quite sure I am internally largely female psychologically, male physically and nearly 60 years into the struggle between the two.
I joined this site in early August of this year. As background, I'm 59 years old, married for over 30 years, have 2 grown children and one 2 year old grandson. I'm an academic physician and researcher at a very well known major university hospital and university with research collaborators at numerous major universities worldwide. I not only run a large, very successful research group but also quite visibly head several key clinical programs and am extensively involved in the teaching programs from medical students to post-doctoral fellows. I have administrative roles in out department, collaborations with industry, and on and on and on. You get the picture--I've got a lot of life infrastructure, a lot at risk for disruption or loss. The curious part of the story is that my wife, whom I love very very much, is a psychotherapist. albeit one that works primarily with children and adolescents.'' Unfortunately, insight she offers to her patients does not extend to her ability to apply those insights to her own life.
From my earliest memories, dating to just short of age 3, I was intensely interested in how things work; later science in general, mathematics, ameteur astronomy and telescope building, things electronic, radio communications adn eventually Ameteur Radio, classical music, art photography and as an adolescent had an obsessional need to learn to draw and paint. As an observation, you will find a disproportionate representation of the scientific and technical professions represented in the membership of this site. I don't think this is due to an attempt to bury the TG urge in a hypermasculine profession. In my own case, this was balanced by a sharply contrasting urge toward things aesthetic and artistic. I never liked team sports. I new I was a bit odd or different.
I am sure there is some more fundamental link. In any case, I ended up with several careers before this one and as avocational interests did some quite serious photography and developed an unusually intense interest in classical music beginning at about age 9. By the time I was in elementary school, it became shockingly clear to me that I tended to easily develop strong friendships with the girls in school, more so that other male peers. This did not seem a problem and caused no problem but was obviously different that most of the other boys. Things changed with hormones--I was uncomfortable with puberty and the pressure toward dating. I understood the girls emotionally and identified with them. I felt emotionally similar to them, very different from the guys. I ended up in a private boarding prep school which fortuitously was at all male. This relieved much of the pressure I felt around puberty allowing me to submerge these perplexing feelings.
I had discovered I had interests in women's clothing and found fascination with typically female socialization, dress, grooming, etc. It was not obsessional, never became a fetish interest, never struck me as "sick" or perverse. I had not really experimented with crossdressing at this time I never had any sort of gay male urge whatsoever. I did tend to have certain very well chosen male friends but they were usually somewhat odd or eccentric in their interests, or had specific interest that paralleled mine academically or avocationally such as in radio or photography. I was never a man's man; not the sort you'd see parodied in the extreme in a date movie, not a "basic bro." On the other hand, I don't think anyone ever suspected me to be gay or having gay gestures or behaviors or would characterize my behavior as effeminate.
As adulthood marched on, I trained myself to suppress much of this uncomfortable gender confusion. I ended up in college with many friends and dating a few women, in each case developing very intense relationships. One was with a wonderful woman that I would characterize as a soulmate but the relationship did not work out. It took me decades to figure out why, though. Both of us had at the time unrecognized gender issues--she, lesbian tendencies; I underlying TG confusion. I ultimately met my wife in graduate school, we married, had our kids, and life went on in the usual flurry of career, moves, family. Mostly, I was highly motivated to date and marry for all the right reasons. I did indeed fall in love with my wife and continue to love her even more intensely today. In the throws of high testosterone levels in my 20's it was easy to follow this trajectory toward the classical family existence, other gender issues almost completely suppressed. Almost. It was about at this time that the first inkling of serious urge to crossdress began. I'd obtain single items of clothing, usually undergarments, which would rapidly generate intense guilt and shame for me that I would "purge" them. This continued for years, only emerging every few years.
It is critical for me to point out that I am not a classically defined crossdresser. Actually, the clothing means very little to me, per se. Other member of the forum will need to allow me some license in what I am about to say as it is a gross oversimplifications to be sure, but one that will illustrate my point. I new I was not a classical crossdresser. I gained not sexual stimulation from crossdressing, didn't do it as an "artform" or performance (e.g. drag), didn't want to use it for female hypersexualization. I simply had an affinity for the idea of expressing internal female identification. It seemed right to dress as a woman since I knew with increasing certainty, that is what I was internally and psychologically. When dressing congruently with my internal gender there is no sexual component for me. I tend to dress like a typical approaching 60 year old perhaps slightly frumpy woman off for the weekend around the house. I don't look like I'm doing to a formal event, not overly made up, not dressed like I'm trying to look like an oversexed 20 year old. For me, the goal is calming, relieving my gender dysphoria, soothing the need for internal gender expression. When the episode is over, typically following a weekend alone, house to myself for 2-3 days; I would often be hit by a tsunami of gender dysphoria returning to my male presentation.
Once the kids were grown and out of the house, pressures of day to day family life decreased, I found the gender issued roared back with a vengeance. I could speculate on the mechanisms driving this emergence--clealry numerous including middle aged decline in testosterone concentrations. Initially, the few items of clothing became a small wardrobe; all hidden away, my wife entirely unaware. How many major cycles of this acquisition-purging? Several over the last about 10 years, each with increasing intensity of guilt and internal emotional strife; each with the soul searching and questioning whether to disclose to my wife. As others have discussed, this is a veritable hell to live in. I have never kept anything from my wife but this. I have never had event the slightest deviation from complete marital fidelity over going on 35 years but this. I see this as a collision of worlds, ultimate conundrum for me internally. I have never had the urge to end my own life over it, but I can easily understand how this leads to levels of internal strife, pain and despair causing suicide. I'm sure I speak for most of us who have replied here.
I wrote all this to lead up to the following. In August of this year, all of this came to a head for me. I found myself working at home on a research paper dressed as "Steph." I was in a period of intense gender dysphoria which I was hoping to mitigate at least to some degree by dressing congruently. It was not working, I was feeling more and more despair. I had read the Susan's forum many times but never participated, surely part of my denial of the reality of my gender discordance and underlying TG nature. I can't tell you what finally led to formally joining the forum but in any case I did, wrote about my "predicament" only to find a community of many like spirits. Several of the forum members offered support and insight that finally gave me the courage to seek psychotherapy and fully confront this reality central to my life. Therapy has made all the difference for me. Unlike many you will meet on this forum, I do not have the body dysphoria that is part of your husband's case. I was able to simply embrace the nature of my personality structure and mainly female psychological attributes without dichotomizing my situation into male vs. female gender. I'd love to get up in the morning and get dressed, interact socially, play out more traditional gender based roles as a woman. Happily, I did not ultimately need to take measures to make this happen.
Therapist come in all flavors and types. I chose one whom I knew would be able to look at my entire situation bringing a somewhat agnostic approach to the therapy. There are some therapists who I suspect are insufficiently skeptical of the diagnosis up front and do not do diagnostic due diligence before forging ahead into plans for transition. This leads to the main point of my post: Not all need to transition; not all can reasonably manage the logistics of transition. Given the complexity of my situation, particularly at work, I could not imaging how I would navigate gender transition while keeping my role intact. With respect to my relationship with my wife, I cautiously probed this question carefully with her over the years without disclosure of my situation. It was very clear to me that her response should I disclose my gender concerns and TG nature would be based on the perception of being victim of a sustained dishonesty and betrayal, one which would overshadow any other consideration, terminating our marriage.
For these 2 reasons I judged it would need to be an act of absolute despiration to transition or even come out. I was fortunate that my therapist offered substantial help to me to come to a better understanding of my internal psychological milieu, also urging me to resume a meditation practice I had abandoned a number of years ago, and guided me to a place where I am pretty happy, not distressed, functioning normally in my work and life as a whole. Whether this will be a sustained solution it to be seen but I am quite confident it is.
If I lived on a desert island, I suspect I would have found the decision to transition fairly easy to make. Given the complexities of real life and the good fortune I had to be able to navigate a non-transition solution that allows me to function and go on comfortably with my life, I chose not to; no, I was fortunately able to avoid it. There were some moments early on when I was becoming nearly resigned to the need to do some sort of transition whether low dose hormones or something else, disclose to my wife, face likely loss of my marriage--just to relieve the unbearable guilt and intense pain of gender dysphoria.
I have only the greatest respect and admiration for my friends and other TG individuals who facing similar gender incongruity have bravely gone on to full transition. Their examples in most cases are nothing short of heroic. A feature which only further intensified my dysphoria and despair when grappling with my gender was the sense of being too weak of personality, feeling too cowardly to disclose and transition. With therapy and the support from the wonderful people on this forum, I gained the insight that I was being far too hard on myself. My decisions were not as simple as questions of bravery vs. cowardice. To the contrary, they were driven by overwhelming sense of obligation to my wife, family and extensive network of student and colleagues. I had determined that I did not need to create the disruption of many lives to serve the needs and happiness of just one.
This was my solution, but I think I am probably one of the exceptions. I am certain your husband has not made this decision lightly. I am sure he would have been very happy to be a "plain vanilla" cis-gendered husband if this were possible. If he has come to the point of disclosure to you and expressed desire to transition, the need is clear.
As others have posted, this is not primarily about you but I assure you, your husband did not make this decision lightly and without consideration of its impact upon you or your marriage. If you love him, try to help him through this difficult time. It is impossible to know the specifics of the outcomes for either of you or your marriage with any certainty at this point. Please do not do that which I am very certain would be the response of my wife, a snap conclusion and end of marriage.