Okay, so what would you do if you were in this situation? Do something, or nothing at all..?

Okay so me and this guy just broke up, & i told him that we should just take a break. Won't get into detail, but yeah we broke up just today, and here he goes adding this girl that he was gonna cheat on me with, and then he added my ex ..how weird is that? So the guy that i just broke up with and my ex they were friends before me and the guy i just broke up with went out..so then my ex hated them and they werent friends anymore..so now im guessing they're gonna write to each other and blah blah probably just say stupid stuff..what should ido? And i saw my ex just yesterday and he kept on looking at me,. idk..weird stuff..what should i do?