Amen to what Pam said.
See, the body is -- uhm -- sex-ized in the first trimester, but the brain is gender-ized in the final month before birth and the first month after birth. For at least 97% of people body sex and brain gender match up. For less than 3 percent, there's some mismatch. Out of those transgendered, less than 1% (some say 0.1%) actually are so strongly mismatched they KNOW something's wrong, or they figure it out later in life.
You are NOT crazy.
You are fairly rare, but that doesn't make you a FREAK.
Personally, I envy trans-guys. They start taking T, and pretty soon they're accepted as male. Trans-girls have it a little harder because the male puberty they had to undergo leaves their bodies, faces and voices scarred with masculinization, which can't easily be undone.
You'll see what I mean when you meet and hang out with other FtMs. You'll feel right at home.
The problem is society is sick, and can't see that one-size-fits-all gender assignment doesn't always work. Start working on your presentation. That'll take you a long ways. Get with a gender therapist. Start working towards getting a letter to start T. Keep your eye on the prize. And every time they ma'am you smile, and mutter an expletive when you're out of earshot (that's what I do...)
You'll get there, dude!
Karen