Why does love have to hurt so much?

I used to think that love was a great and beautiful thing, but I'm starting to think much differently! I've wanted this guy for more than a year now, but he has made it (somewhat) clear that he does not want me back, even though every time he sees me he stares and he hits on me very subtly. After we had first met, I thought I had made it clear that I wanted to spend time with him, but he just ignored that (no answer is my answer, right?). The thing that drives me crazy is that when I'm around him I can feel that weird ual tension between us, and I know I'm not making it up, and I know it's not just coming from me. It upsets me that there might be something there and yet he still rejected me. I keep trying to get over it because I hate this hurt, but maybe part of me doesn't want to get over him, part of me still wants him. I just don't know what to do anymore, I'm so tired of feeling so sad about the situation, and I've never hurt this bad before. Please help, any advice would be very much appreciated!