Dunno about the 'mental disorder' bit...
Anyways, I have a friend who's pansexual (bisexual but also likes people who dress in other sex clothing) and feels like you do. I'm very close to him, as I honestly don't know entirely what to make of this, but as he usually just wears men's clothing it hasn't yet come to a head. I've accepted him as he is, but am still wary. I don't want to sound horrible but it's because he's different, I don't know what he'll do next. There are no limits set, like with everybody else. He's not universally accepted, his parents have no idea, most of the people in the college are 'weirded out' by him, they don't know what to make of him so stay away.
I hope by expressing my views on my friend and why I feel this way will help. Having a definite gender also helps. It relieves some the insecurity. My friend dresses his gender mostly, so I know to react when he''s like that, but when I see him out of college in girls clothing I still like him as a friend but I feel must less secure and, dare I say, maybe a little 'weirded out'. Because of the sudden change, the '360'. It threw out of my comfort zone and put me off tilter.
Hope this information helps. I try to keep an open mind. Not everybody is like that. Anonie xxx