I'm a boy but always felt like I should have been born as a girl... I'm really confused?

I am a guy and since I was little I've always felt like I should have been a girl. I have a girlfriend of almost a year and even though I've always tried to ignore it, it keeps getting harder to. Just to clarify, I don't like guys in the sense of a guy with a guy. However, when I think of a guy and a girl, I would rather be the girl. I would rather snuggle into a guys chest than hold a girl against mine. I never really had NEARLY as strong of a drive as other guys. What I've noticed is that girls don't turn me on, but rather the thought of being the girl turns me on. About the only thing that turns me on is when my girlfriend gets "excited" or when she runs her hands through my hair while making out or any other action normally ociated with the woman. I'm just super confused. Someone help.