Ugh why me

So me and my SO love eachother alot. But i keep finding out that in the past hes slept with alot of girls i know. Were from a small town. Well there all skinny and pretty and im over here with no make up and fucking fat and i dont like that my friends know what my bfs dick looks like. I hate it and im beating myself up over it. What should i doooo to just stop thinking about it. I didnt even want to have sex last night or this morning. I want to cry.