Is he treating me right?

I have a boyfriend…weve dated…hmmm I don’t know…almost more than a year. Once we got passed the whole “happy happy joy joy” months (you know when he’s all you ever think about…ever!) Well we changed. He wanted sex all the time…but I wasn’t willing to give it too him. I dont like to let people down and he knows that. Everytime I would say no, he’d get this disappointed look on his face and I’d give in and let him do whatever he wanted to do. Friends tell me he’s using me for sex but he can be really sweet sometimes. At school and in the halls, he’ll tug me around. Yanking me one way and then the other. I tell him to stop but he never does. It got to the point where he yanked me so hard that I tripped and almost sprained me ankle. He apologized and he stopped yanking me for like, I don’t know a few weeks. Then it started up again. He’s such a little kid sometimes. If I dont sit as close as possible to him in lunch, or when were hanging out…or in class. He goes, “Fine dont sit next to me, I’ll remember that later.” or “Guess you dont love me enough.” In the end I always scoot closer. To clear this up, he’s never hit me. And I dont believe he would…tho he is pretty rough with me sometimes. He’s always talking about my looks and my body, never about my personality and he shares our sex life with the world. It makes me feel like a slut. He wont let me hang with friends unless he lets me, he gets mad if I dont call him ALL the time and if one guy so much as looks in my direction he goes violent. I dont know what to do. I’ve tried dumping him twice but he’s the whole, “I’m gonna kill myself type” so I end up going back because I feel bad for him. I dont even love him anymore, atleast I dont think and it keeps getting worse. I need to figure out what to do before it gets bad. Is he treating me right? Should I leave? What people?! I need help.