Help?

I went out drinking on Sunday night with my best friend and met up with her friends. He bought us both a drink, I only had 2 margaritas that night but we pre gamed a lil in the car with vodka and sprite so i was feeling good and I'm already a light weight.. Anyways we're having a good time and I start talking to some dude next to me and my friend goes to a table so I say hey I'm going with her and don't remember anything else after that. Totally weird! Then ended up waking up in my room butt naked and some dude laying next to me! I was tripppinn balls. I was like wtf why are you here how did I even meet you? And he said i sat next to him at the bar and insisted to come home with me? I really dont know. Then he told me we had sex all night and i went down on him and everything and I don't fucking remember shit!!! It's so scary to think that I can't remember anything and I wasn't that drunk. Do you think if I had something slipped in my drink or something this would happen.. Like blacked out? Idk but it's so weird to me that it happened and i dont even remember getting inside my house. So he undressed me and did what he wanted i dont fucking get it. Then i notice i have 2 bruises on my arms and knees. Idk what it could be and I think its weird that my friend I was with doesnt want to help me try to remember what happened