I think I might be a transsexual.
I'm biologically male, at least, early 20s, lifelong "pansexual"
(a clumsy and irritating term, but more pedantically accurate than "bisexual"), engaged to marry a pan/omni/bi/whateversexual woman. And mentally, emotionally, what-have-you, I feel like a slightly-tomboyish girl with a dick.
I've always been very feminine, even as a small child: I learned to pee standing up but continued to sit, in emulation of my big sister, and talked my mother into painting my nails at every opportunity (to my father's chagrin). At the age when boys are terrified of girl-cooties, my entire kindergarten social circle was female (I had little crushes on them—but I had little crushes on the boys, too). My ever-chagrined father had to stop me from carrying a purse. I preferred Nancy Drew to the Hardy Boys, Barbies to G.I. Joes—I'll spare you my whole life story; you can probably figure out the rest.
I relate to others in a very typically-female way, and relate to women with uncommon empathy; I have and have had countless friends treat me like "one of the girls," above and beyond the gay-best-friend paradigm; I find women's fashion infinitely more interesting and appealing than men's. I'm frequently mistaken for female on message boards and the like, and apparently my short fiction and poetry "read like a woman's," whatever that means.
I doubt most of that was necessary; let me cut to the cliché: I suspect that I am, and have always been, a woman trapped in a man's body. This is what I am Asking MetaFilter:
1) Is there a way to know for sure, one way or the other?
2) Is transgenderism something you even can
wonder about, or is it an "If you have to ask, you're not" kind of thing?
3) All the resources I can find are aimed towards people who've already figured things out; can you point me at information geared towards people in my position?
I'll post answers to important counter-questions through jessamyn, if she doesn't mind, and you can contact me by email at email@example.com if you'd like to discourse privately. Thanks in advance.