My step brother abused me sexually. how do i handle this?

We had developed a pretty strong bond and also a pretty big crush on each other over the years. None of us had acted on it for the obvious reason. I now live in a dormitory and he has a house of his own, but we visit each other very often. Last weekend we got drunk, watched a movie with a few bed scenes, one thing led to another, so we made out and actually started undressing each other. Halfway through I made an effort to stop myself. I said ‘no’ and asked him to stop. I’d like to leave out the graphics, so let’s just say I was physically ready for sex and he could tell, given all the touchy-feely thing. I was determined not to risk our relationship, but I didn’t hit or scream at him, maybe silently shed a few tears, that’s it, which he may not have noticed because it was dark. It didn’t hurt or anything, and despite my frustration and disgust, it actually felt good. This is what I can’t explain to myself. The entire situation does not fall under my idea of assault, but why then I’m feeling so abused and angry as hell? I left, now he keeps calling and texting. At the moment I don’t want to talk or see him. I don’t even know what I need exactly. I don’t think an apology or anything else for that matter would resolve the issue. I still love him very much and I will not break things off with him, although I strongly believe he had wronged me. But I know he also loves me and he had always been doing everything to make me happy. Example, he is paying for my expansive school. Clearly, I’m confused, I try to find explanation to this situation and it’s not going so well. The best idea I could come up with is going to therapy together. Anyway, I think I could use some good advice.