Hi Becky,
I'm so glad you found us! What you've posted here sounds so much like the emotions I went through when my husband told me that he(she) needed to transition...after so many years of INSISTING that nothing would ever change, and that he'd(she'd) never need to do anything with these transgender feelings.
It can feel like a betrail but know that at the *time* that those words were said...they were likely said with *absolute* honestly. Many (if not most, if not all!) trans people feel they can "beat this" and keep going in the life of their birth sex.
If you choose to embark from here on this journey through gender transition there will definitly be high parts and low parts. My advice to you would be to be as honest as can be, without being brutal. (though sometimes...brutal honesty can be needed!)
Your feelings are valid, they are important and you need to make sure to take time for you. I'm glad to hear that your going to therapy. That's wonderful. Check and make sure that this therapist has worked with transgender people, and preferably has worked with spouses of trans people before as well. The needs, the feelings, the processing is very different and important. The first therapist I went to had never had any trans clients and kept reminding me of how important this is for my spouse and how supportive I *should* be...it was horrible and made me feel even worse...rather than moving forward toward *being* supportive. I dumped that therapist and found someone really really wonderful who's helped me be supportive, allowed me to vent all my feelings and frustrations and work through them.
From the outside (and perhaps from the inside as well...) transition moves both so slowly...and so so fast all at once! While I don't want to scare you, or make you feel like you can't do this, or shouldn't do this... (as that's only for you to choose what you need in life and what you can handle) transition really does effect *everything* about your mate. It's not just the physical that changes. It's the mind, the senses, the skin, the feelings, heck...even tastes and likes/dislikes in food!!
However...it's a beautiful thing to watch someone bloom into themselves. To really release the biggest stress they've ever been packing around...and what a gift to *you* that your welcome into this scary, frightening time of walking into the unknown. That you are trusted, and a safe, welcoming person. Truely it is a gift to be present (even when it doesn't feel like it.)
I've gone on quite long enough....please, don't hesitate to private message me if you'd like. (Private messages can be exchanged once you've posted 15 times.) Keep posting, keep talking, keep being honest and keep taking time for you.

*huge huge hugs*