Meant to be with his ex?

To make a long story short, my boyfriend chased his ex for like 7 years and when he finally did get the girl she treated him like shit. And I’ll be honest, when him and I got together, we were about 4 months in when o caught him talking to her again. We broke up about a month after that and eventually worked things out. We’ve been back together for about a year now but ever since then I’ve just thought maybe they’re meant to be and they’re just too young for it to work right now. But I’ve also thought that maybe I just think this because of my anxiety, especially some of the anxiety resulting from bad past relationships (cheating). I’ve quite literally thought about ending it because of this so many times but I don’t even know what I would say. I’ve never even brought these thoughts up to him before. I’ve never even said anything to my therapist about it actually. I just let these things float around in my head and stress myself out. I don’t really know what to do. I honestly do think this is just my mental health affecting me but I’m not sure at this point. It could be anything.

Dude note before anyone says he may be lying to me about how awful she was to him: we live in a small town and everyone knew how she treated him. His family said it, his friends said it, her friends said it. It was a well known thing.