Posted this already but need help still!!

So I was dating this guy for 5 months and we broke up 2 weeks ago he said he just wanted a break and that he still wanted to be together we still talk on Snapchat as friends, he asks if I miss him and I have been hearing that he’s talking to a junior when he’s a freshman just yesterday I saw they were together on Snapchat maps he text me while they were together saying not to talk shit about the girl he was with or see what happens. I want to get back at him because he’s so rude to me and wants his new bitch to fight me. Idk what to do any suggestions??