I'm a guy interested in receptive anal sex: does that mean I'm gay?

I'm a 16 year old boy, and for as long as I can remember I have been attracted to girls and yet rarely able to feel comfortable around them and get to know them. I've always been a nice person (the friendly guy) but without that many actual close friends who are girls. Recently I've noticed I am turned on (and everything that follows that) with the thought of receiving anal....