It was rape.. The fact that you told him no, means that it was not consensual. You should tell someone hun... You may not want to because of the "problems" it can potentially cause; but this could have long term affects that aren't fair to deal with, and it's better to get help now. And he shouldn't get away with what he did to you. No means no. It doesn't matter if you may have been kissing and flirting prior; you told him you didn't want to, and he didn't respect that. Your lack of fighting during it has nothing to do with it; he's still completely at fault.
If you really don't want to tell anyone about it, just make sure you don't bottle it up, okay?
PM me if you ever need to talk =)