The other night, he invited me to his place as he was having another bbq, and offered that I spent the night. I agreed, but he told me no one could know. I didn't think any more of it, as when I stay longer things usually turn into a party (i'm not sure if that is why he didn't want me to say, or if it was so they don't assume that he and I were gonna do anything).
He throws up that night, and I kind of massage his back and take care of him, as a friend does. We start to kiss later, but I tell him nothing can happen because he has a girlfriend. Thirty minutes later, we had sex (consensually, I think I'm even the once who initiated it again, not sure tho). Our very close friendship has not changed one bit, it's only maybe a little bit less flirty, although I haven't seen him since (it's been three days)
He told me he was not telling anyone, and didn't regret it or feel bad at all. He told me I could tell my best friends, as he knew I would, but that no one else could know. Some of those I told said it was not my fault, and that he's the one responsible, but one of my friends told me I was a homewrecker, and that I could tell from the start that he wanted to have sex with me, and that our friendship remains the same because he wants it to happen again. Is this person right? What should I do? I really don't want to lose my friendship to him.