I don't even know what happend

Me and my girlfriend were dating. Things started to go bad in nov mid and we started getting distant .....things were fine until January, i broke up and went no contact. Today after almost 10-15 days my crazy ass just wanted to check her profile idk why and I found out she followed her ex back(they broke up a year ago and didn't speak). I don't know if I got cheated on , i just found the are following few hours ago. The thing is I don't think so that a relationship that was ended a year ago would come back in 10-15 days. Did i really get cheated on? Should I confront her about it?