I'm kind of in a similar situation as you.
I'm a girl, but I've never acted like a proper girl.
Maybe it's because my first best friend (when we were aged 4-5) was a boy and when I went to primary school I was in a gang of boys for half the time there.
But then I went to an all-girls secondary school - and I never felt so out of place in my life!
I mean yeah, OK, there are such things as tomboys, but I literally WANT to be a guy....I just don't know why.
For example, I walk into Topshop or somewhere and I glance at the girl's section and I just want to puke. I just hate it.
I look at the boy's section and there are so many items of clothing that I want. I seem obsessed with boy's t-shirts and jeans and I have always worn mainly boy's clothes. I do not give girls' clothes a second look, unless it is a decent t-shirt.
Though when I wear my boy's clothes, I don't actually want to be manly and look like a lesbian, and so I'm kinda stuck.
I just want to be a guy so I can wear 'nice' clothes comfortably. Sounds vain doesn't it?

But I'm not vain...I don't care about personal appearance; I just like wearing what I like.
I also hate girls...like, not each girl specifically, but the idea of being a girl (make-up, manners, dress sense) just annoys me and I just cringe at the thought of it.
I walk like a man (well, not extremely manly, lol), dress like a man, talk and swear like a man, have never worn make-up in my life and am generally so like a guy sometimes, that I wonder if I was born the wrong gender!
I suppose my feelings are just superficial, but some days I really do wish I was born a guy.
If I could wave a magic wand, I think I'd transform myself into a gay guy - I'm not a lesbian, and I find men attractive (so I know that my 'girlness' is still there!).
Argh. Sigh.
....Sorry for hijacking your thread Anon#1....I just saw you were in a similar situation and wanted to rant.