Not working.. and upset

Last night my boyfriend and I had sex in cowgirl position and it didn't work I've never had this problem before. Knowing it didn't work for me he ended up making it worse by saying it was my fault in a joke. As of right now I don't want to have sex anymore. I am deeply hurt by this because I already hate the way I look. Today he was like it was fine he still enjoyed himself and not to take it so personal. I'm thinking to myself how can I not.