I was in this position 3 years ago. I was dressing fully in secret but one day realised that my bag of makeup was not with the rest of my stuff. I searched the house (not well enough as it turned out) without success and then realised that the items had probably been found so decided to confess all.
My wife went through a rollercoaster of emotions from very upset, feeling cheated (we'd been married for over 20 years), mild amusement, supportive (she came home with a padded bra for me one day), interested (she told me to come home from work early, ran a scented bath for me and had my things ready for me to put on.
Unfortunately, while I was dressing for her, her expression gradually changed and I could see that things were not going well. Shortly afterwards, she became very hostile to me and finally said that she didn't want to be married to a woman, I looked ridiculous, I should get rid of everything (which I had offered to do to save our relationship) and, if she ever found anything of this sort in the house again, she would throw me out. Other than that, she was supportive!
At this point, I should say that there was periodic hostility in our marriage prior to this episode and it continues to this day. To be honest, the marriage has probably lasted through apathy, unwillingness to lose what we have and the overriding desire to provide a proper family life for our kids. What I am finding is that my desires and urges are beoming stronger by the day to the point where I'm now starting to look at transition as a viable option - however, there are of course barriers to this - apathy, unwillingness to lose what I have and the desire to provide a proper family life for my kids - a familiar ring?
From the advice I have received directly since joining this community a few days ago and also from reading other posts, if your spouse truly loves you, you will be able to work things through; your relationship will almost certainly be very different at the end of it, though. In my case, any confession of how I feel now will almost certainly bring a swift conclusion to our marriage but, as we've both given up trying to work on our marriage, this may not be such a bad thing (unless, of course, the kids get dragged into the battle).
As others have said here, follow your heart and your female intuition. Only you will know the depth of your relationships, not only with your spouse but also with your friends and colleagues but, in all honesty, the friends who drift away as a result probably weren't real friends in the first place.
Good luck,
Amanda