Hello Emma,
Welcome to the forums. I wish it was under better terms.
A lot of members (including me) told your fiance he had a duty to you to come clean. Personally, I would not have chosen the path he took, but it's done and it can't be changed now. He made it a lot harder on you than necessary, and he's very lucky you chose to stay.
It's my choice to inform any girlfriend I may have sooner rather than later, and long before popping the question if I do the asking. The same goes for her if she has any ideosyncrasies. The only thing that's non-negotiable for me is they be at worst harmless. Drug and alcohol addictions, for example, are non-starters.
There is a genuine ladies (female at birth) section for you once you have 10 posts to your credit. I'm sure they will welcome you with open arms. They have had some issues with crossdressers obtaining access, so you'll have to jump through a few hoops to get in.
Dressing in the spouse's things is very much frowned upon here. He should have at least got his own stuff. Most of us see it as an invasion of the spouse's privacy.
There is a lot of material in the Loved Ones section for you to read. Here are two threads you and may find helpful:
http://www.crossdressers.com/forums/...ad.php?t=90231
http://www.crossdressers.com/forums/...ad.php?t=12890
There are reasons CDs don't tell their spouses. The biggest single one is they are absolutely terrified of their reaction. In some cases, the relationship failed and the female half went on a vindictive rampage. Keeping children from their father is not uncommon. I won't name names, but their stories are on this and other similar forums.
The typical crossdresser is very much like a male who does not crossdress. Wanting prosthetics or other padding to give us the appearance of a more feminine form is very common. Most of us don't want permanent changes to our bodies apart from ear piercing. Temporary body hair removal is also common. Less common is permanent body hair removal.
From time to time you may hear of a crossdresser committing various crimes. These comedians contribute to negative stereotyping and do not represent the majority. They are criminals who happen to crossdress. The media seems to like sensationalising the crossdressing because it sells.
For my part, crossdressing is primarily escapism. I'm the first to admit it isn't realistic, but it works for me. I have no interest in going out in public beyond a very private backyard, but there are plenty that do. I also have no interest in hormones or surgery beyond ear piercing. I would like a pair of breast forms suited to my body and some hip padding. The drag queen look does not interest me. I prefer to appear as a dignified lady.
You do not have to accept this. It is entirely your choice. Frankly, it's better you found out now rather than five, ten, or more years down the road.
It's my impression, correct or otherwise, that the two of you have some trust issues to work out and probably some others as well. If necessary, put the wedding off until both of you are satisfied these issues have been addressed.
If you're afraid he will want to become a woman, you have the right to insist on a referral to a licensed, nonjudgemental gender counsellor or a psychiatrist, but stay away from anyone advocating reparative therapy. It is essentially repression, does more harm than good, doesn't work, and is just as unhealthy if not more so in the long run as a judgemental counsellor. Gender issues are more nature than nurture, but sometimes nurture exerts a powerful influence.
It's important to realise a counsellor can only provide an educated guess, not a guarantee.
If you decide to accept his crossdressing, it's a good idea to negotiate boundaries about what you're comfortable with and insist they be respected. Please recognise the crossdressing is part of him and won't go away, and an attempt to shut him down will only cause resentment. An external real-life support group has value, both for you and your fiance. Some may ask that he dress from time to time as evidence of crossdressing. Crossdresser clubs often have resources available for both crossdresser and loved ones.
If you cannot accept his crossdressing, it is probably best for the two of you to part and find other soulmates.
Good luck.