Am I overreacting!?

I told my bf my ex, (been an ex for six years) that he sometimes messages me on Snapchat and if he had a problem with it I’d delete it. He said no it’s fine as long as you respect what he have then more power to you. I said okay thank you. He then proceeded to tell me he talks to some girl a few times a week and she has a bf and he knows they talk and they they’re just friends. Idk but I got so jealous 🙄 I mean obviously I can’t make him stop and I wouldn’t ask him to but man it really bothering me😢