Cheated on me and Blocked Me

I was in a relationship with a guy for a year and a half. At first we were not long distance but then he went away to school. But regardless, he gave me attention every day, always texting me, FT'ing every night. I had no suspicions he was cheating. He introduced me to his whole extended family as his girlfriend, and all of his friends I met. A few months into dating him I saw messages from a girl, he told me she was a friend and I could meet her if I wanted to. I wanted to trust him so I said no and he said he blocked her and wouldn't speak to her. Everything was good after a while I just became a little more suspicious and insecure. Recently he came back home, and I saw a notification from a dating app. When I asked him about it he denied he had one. I decided to make a fake profile on the app and find his profile. I found the profile and it said that he was looking for friends. I had peace of mind but just a little suspicious so I let it go. Then recently I got insecure and wanted to be sure that's all it was I messaged him on the app. He instantly started flirting with my fake profile, asking when we can meet up and outright denying he was in a relationship. When I told him I caught him, he blocked me on everything and has not been speaking to me despite my numerous attempts to reach out. I logged into his Instagram profile and found he was talking and flirting with multiple women the whole time we were together. His ex even reaches out to him to get back. I need closure