Why do I feel this way?

There is this guy that I have my homeroom with, but I had choir with him last year as well. Whenever I see him, my heart just flutters and beats faster. I am usually uneasy around other teenage boys, but this one, I am somewhat comfortable with. I smile after I talk to him. I don't think I've ped more than a hundred words with this boy in my life, though. I think about him a lot. I had a crush on him last year, and some parts the year before, too. If this is a crush, what can a do to stop this feeling? I also get a feeling in my privates when I think about him. I look at his profile on Facebook, too. A lot.