Cheated??

So my long time boyfriend and I broke up the other day..he broke up with me. So I went to a friends house and she took me out drinking... well she took me out to get blacked out. I don’t remember anything but somehow I ended up at a guys house that I know, he is a friend that I don’t know very well and I because I woke up with clothes on I figured nothing happened.. well he just told me shit did happen. And now my long time boyfriend is acting super sweet and doesn’t want to break up anymore. I’m so fucking confused and I cannot believe my so allied friend would allow this to happen! Why would she let me go to this guys house! She knew I was fucked up! She was the one saying she was going to take care of me and that I was going to hang out at her place after the bars! What the fuck do I do? Just pretend nothing happened and try to fix my relationship?