Most Helpful Guy
Sometimes the only really strong connection between two people is sexual. They may care about the other, respect the other, but just find that the nonsexual chemistry is lacking but the sex is still great.
Many years ago, I was really head-over-heels about this girl but she ended the relationship. We ended up hooking up for still excellent sex, and after I got over the hurt I realized that she was right. We had too disparate goals and personalities to really work as a couple, but we always respected each other and had great physical chemistry.
It happens, and as long as noone is being manipulated or mislead, things should not be too painful and may end up with a more stable friendship.
Most Helpful Girl
It could just be a phase. I went through something similar with my own boyfriend... we started with the chatting, working out, just hanging out together. Once sex came into the picture, we'd do basically nothing but have sex together. Sometimes even skipping class just for that. A few weeks passed of just that when I started asking myself the same questions you seem to be asking. I loved sex and still do, don't get me wrong, but I've never been interested in just that so I mentioned it to him and insisted that we set aside a day where we just hang, nothing more.
That seemed to be enough for us. Tel your guy how you feel! It's easy to get caught up in the hormone rush, but make a point of taking just a little bit of time regularly to nourish the actual relationship.