Lost Lady,
First of all, welcome to Susan's. I think that you will find people here who will listen and help you.
First of all, I feel sorry for both of you because you're both hurting. Your husband is hurting because he see's how hurt you are. Then you see how hurt he is, plus the weight of the upcoming changes in your life, and then you hurt. It's a vicious circle. You BOTH need to seek therapy NOW before either of you threaten to hurt yourselves again.
One thing that I want to point out - the "he" that has always been there for you will still continue to be there. That loving person inside won't change. In fact, if the conflicts are resolved by coming out and going through transition, the "she" that will result will be far happier and less conflicted than "he" ever has been. You may end up with a closer relationship in the end.
But, it will involve you being able to let go of the "him" in order to embrace "her". Yes, that's tough - really tough. But you have to remember what I said - that person that you fell in love with and had a child with is still there - just in a different package physically and emotionally. I would imagine that all "she's" looking for is acceptance of "her" by you. "He's" been struggling all this time trying to keep a secret and now that it's out, probably feels not only the pain of changing "himself", but additional pain to see you struggle, as well.
Once you make the decision to accept "her" and decide that "this is going to work out, no matter what", then I think that things will be better. Do you remember the part in your marriage vows "in sickness and in health"? That's commitment, pure and simple. The change in your lives will involve commitment on the part of BOTH of you. You'll both need to sit down and have a talk and say to each other, "We're gonna see this through, no matter what. We love each other, and that's what's important."
But again, you BOTH need therapy. "He's" experiencing all of the changes and you're grieving AND having to deal with the changes as well. Every person who goes through this needs help to make it. The fact that this hurts so much is merely a measure of how much you care for each other.
Keep your communication lines open at all time - BOTH of you. Each of you need to know DEEPLY what the other one is feeling at all time.
Please write again. That's what we're here for - to support and help each other. I will be thinking of both of you.