How am I ever going to forgive either of them?

So there's this guy that I'm crazy about and we've had a thing for like 4 months. I was gonna go hangout with him last night with a bunch of people but I couldn't because I was sick with the stomache flu. They all got drunk and him and my bestfriend hooked up. I feel so betrayed by both of them. My friend apologized and said she was just drunk but I'm so mad and I can't stop crying. I mean I know me and him aren't officially dating but it's messed up to tell someone you love them and then hook up with there bestfriend. He's the one who called me and told me about this and he was like I'm sorry but I just kept quiet cuz I was crying and then he was like but in a way I'm not. I just don't know what to do or think right now. I need some advice.