Cheater?

After being broken up with because he "didn't want to be in a relationship anymore" he said moves onto a girl who I have been worried about the whole time we were dating. He was my first love and it hurts like shit. Apparently while we were dating I was on a missonary trip and he went out with this girl and some of my friends and they were being very touchy and close IN FRONT OF MY FRIENDS! I just found out about this today it's been 3 months since the breakup. Did I get cheated on?