***Ok this is kind of long, I'm sorry***
Ok well I went through this same kind of situation this semester. I began hooking up with a guy I had liked since the very first semester here at school, so that's two looooooong years.
We hooked up for months, and my sisters HATED him, they'd talk to him at bars and stuff and he was just always a complete ass to them, and he was to me too. So I guess in that respect our situations are different. The thing is, I thought I was ok with whatever happening as long as I knew that at the end of the night, I was the girl in his bed. I know that sounds AWFUL, but I really thought it was ok and it could work out that way. Boy was I WRONG!!! He told me he didn't want a relationship w/me and basically told me he was just using me, and I didn't really understand that b/c it's not like we ever had sex or anything, but whatever! He took up so much of my time though and just drained my emotions. There are few feelings in the worls that are worse than caring about someone SOOOO much and not having them care about you. It SUCKS.
Lucky for me my ex boyfriend came back into the picture, and I still cared about him a WHOLE lot. We worked stuff out and now we are back together so that gave me an excuse to stop seeing this guy and ultimately realize that he didn't treat me with respect or anything and I wasted a lot of my time on him.
Now that I have a boyfriend though this guy has gone completely psycho and calls me/text messages me at LEAST 4 times a day, every day. So yea, it seems like guys like this don't necessarily want you but they don't want anyone else to have you either.
If I were you, if even just one teeny tiny part of your heart is having doubts about this, PLEASE get out of the situation before it's too late. This semester has been a living hell for me and I wouldn't want anyone to have to go though that if it could be avoided. Good luck, let us know what happens.