Moving on and making new friends?

My ex cheated on me. We go to different colleges and he has a huge group of friends and has been dating the girl he cheated on me with. 
I'm so alone. He was my best friend and now I can't talk to him. He doesn't seem to care and he gets to be happy while I'm in so much pain. I still hurt so bad and I'm so alone. I don't have a group of friends who spend time together regularly. I don't have any friends who ever ask me to hang out with them on the weekends or anything, even though I try sometimes to hang out with people.
How can I move on from him? How can I make new friends and have a group of people here at school who can help me feel like I'm not so alone?