Shit. it doesn't matter if he is single, married or your goddamned father. Rape is rape. And that shit is not acceptable.
OK, I can see why you are reluctant. Let me guess - one part what is the boyfriend gonna do to two parts shame, right? Damned stupid, but also totally human.
First things first - you report this asswipe. Not to your boyfriend - to the police. It is too damned late for physical evidence, yes, so it is his word against yours. You know your word carries as much weight as his, right? So get the scumsucking twat reported.
OK. Deep breath and calm down. Sorry, I ain't shouting at you, I am shouting for you.
There are somethings that a guy just doesn't get - this is one of them. I don't know the words to use. I can not. All I can say is use the same technique that is always used for bad news: one word at a time.
But tell your boyfriend you must. You owe that to you.