In the first instance, it sounds to me as if you're saying that you knew he liked you last semester, but you liked someone else and therefore went with the guy you wanted more. After all, you did say "I didn't know how much he liked me." I interpret what you say as meaning "I knew he liked me but I didn't realize he had it bad for me."
You know what? Fair enough. We're not all mind readers. If he feels like he got burnt by you, well ok, maybe he should have confessed his feelings for you and made it very clear. It's not your problem if they guy kept it to himself and you went off with another man.
However, you may not be telling us the full story. You chose to use the phrase, "I totally screwed him over". It sounds like you might have known more than you're admitting and you really did hurt the guy by totally dissing him for someone else. Are you being honest with us?
Either way, it's not unusual for someone to feel angry or hurt if they feel they got the major brush off. He may very well have said those unattractive sounding things to you just to make you feel hurt the way he feels hurt. Though, I have another question for you....
What does "stuff happened" mean? Does that mean "I was drunk and I went to his room and we had sex?"
I mean, I'm gonna give it to you straight, you need to be honest with yourself, he needs to be honest with himself, and you both need to be honest with each other.
This is like high school antics here.
Sit down with the guy and very honestly and gently ask him about where you both stand with each other. You might even like to apologize for perhaps hurting his feelings when you didn't realize he liked you so much. If he says that he stands by what he said before (not wanting a relationship etc) then that would imply that there's no room for you at all...or at least he only wants sex from you. If a purely sexual relationship is not what you have in mind, then it's over and done with, right? He doesn't have anything else to offer you.
If he's wondering why people are calling him a "slut" then maybe he needs to rethink how he's conducting himself. But that's not for you to deal with - he needs to figure that out on his own. What you need to do is simply clear the air so that you can make a decision which is best in line with what you want out of life and in a relationship.
Best of luck to you.
.....Kelly