What’s wrong with me?

Okay. So I’m in a super healthy relationship with a guy who makes me happy. I never thought I was going to get that again after my last relationship. My ex was addicted to meth and was verbally and emotionally abusive toward me. I can’t stop but thinking about him though. He pops into my mind all of the time and I don’t know what to do. I just creeped on his Facebook from an old profile I had and found out he’s dating a girl who used to bully me hardcore in school. I don’t know why I’m so upset about it. I don’t know what’s wrong with me. How do I make it stop? I love my new boyfriend so much. He is my entire world. Helpppppp

Update: the new girlfriend just messaged me to tell me that she’s pregnant with his baby and that I should leave him alone. I haven’t talked to him in months. 🤷🏼‍♀️