Ex dilemmas

Girls I'm so conflicted. Four years ago I dated a guy who cheated on me. He started dating his new girlfriend and they both make fun of me since they think it's hilarious that I cried when I find out. I'm a senior in highschool by the way

Now, everytime I see them in the halls they always try to show off even though it's been three years and I've moved on and am in a relationship where we fight every four months (we just celebrated 2.5 years).

Everytime I am around my ex he keeps saying his girl's name really loudly and making fun of me and "bragging".

They both cheated on each other, and I think the fact that I'm in a healthy, happy relationship is why he does that. I just ignore it and look at my phone. Why is he doing this? It's been years

He definitely doesn't have feelings for me (thankfully)