Advice

My ex and I were together for 3 years. He was abusive through the relationship and would hit, kick and choke me etc. but there was times when we were good and he was really nice. He cheated on me by making fake accounts and messaging girls. He left me because it wasn’t working out and he had 2 different girls in the space of 2 weeks of us splitting up. One of the girls he is with now, he’s 22 and she’s 17. They post and look really happy and I’m upset because why does he deserve to be happy with someone and I don’t. Am I wrong in feeling like this?