Is my relationship abusive?

So here is the deal, I feel very every other way on this. He's my first boyfriend. We've been dating for a year and almost eight months now, I'm 18 and he's 19. Everything was wonderful in the beginning, dreamy, peaceful. Honeymoon like. Three months in, he went to do drum corps, which for those who don't know is marching band on steroids, and during that time we were away from each other. He was practicing music and visual every day all day for the entire summer, most of our connection was through text. He got very stressed, and easily angered. He started asking for things from me sexually that I didn't want to do, but ended up doing for him because he was stressed and angry and I wanted to make him feel better. During the next school year, he went to college and I stayed doing high school, and our relationship was strained more. We kept having fights where he'd break up with me, I'd cry because I felt like it was all my fault, and he'd frame it as my fault, and then he'd come back to me after I'd swear I would change. I wanted sex less and less, and he was still wanting me to do things like send pictures, write stories. When I said I didn't want to, he'd get upset and threaten to break up with me. Cycle, and repeat. This summer he went to drum corps again, and it got really bad. Every concern I voiced to him about it, he blamed me for not doing anything to change it and for not listening to his advice. Then, the band season ends, and we go to the same college. I see him more, and I feel better about sex because I don't feel shame from my mom anymore, but I keep thinking about his manipulation. Is he going to do that everytime he's stressed? I tried leaving him, but I couldn't do it. He isn't awful, he can be so loving and sweet. He takes care of me in so many ways. I feel so weak, and I don't know if I'm overreacting or if I'm right. I don't feel abused, I don't feel like I've been raped, but he's definitely coerced me into sex and sexual acts more than once, and it makes me feel like shit every time. I still love him. Should I? I think about him, and I think about all of our good memories, and all of our love, and I don't want to throw that away, but I know that something isn't right and I don't know exactly what to do. It doesn't always feel wrong, and when it does, I feel like I can just live through it...advice would be appreciated, especially if any of you have had similar experiences. Thank you.