Am I asexual? Can't feel anything unless I think REALLY hard.

I am 17 and seem to be incredibly confused about sexual arousal. I did not try masturbating until my cousin told me to try it at the age of 15. Up until then, no thoughts on masturbation had ever entered my mind. When I did try to masturbate, the content did not arouse me. I would physically stimulate a boner, but unless I thought really, really hard, I would be jerkin' my junk for an hour with nothing happening. I've even had to revive a boner several times. I've tried all kinds of content. All. Kinds. You name it, I've tried it. My close friends know of my situation and just think that my intelligence makes me unattracted to the basic, carnal nature of sex (I'll admit, I'm pretty up there in class rank). But I don't think this is it. I'm human too! I like women, I like the idea of sex, but nothing comes out of my dry faucet. Any way to address this issue?