I don't know what to do

I've been with this boy for over a year now. He got drunk and cheated on me at a party. At his house. In his bed. With a girl that I have to see every single day. He says they just kissed but that doesn't make it any better. I love him with everything in me and I believe that he loves me and that people make mistakes but I don't know if I can go back to him. I've never felt so broken in ny life. Everything feels worse without him though. He was my best friend. I just want advice, please.