I Just Found Out My Bf Cheatedd?? (short)?

I guess technically he cheated on her with you, and is at the same time cheating on both of you. So have him come to your house and be nice to him, tell him to look at this funny thing you found on the net. Show him the FB page that is your proof, then tell him "get the hell out or I am going to call the cops IT IS OVER!!!!"