AIO to boyfriend's Snapchat habits?

Need an outside opinion here! Been with my boyfriend 3 years, we're both in our 20s, and every time I see him he has notifications from girls on Snapchat. I've asked him about it a few times because I found it a bit weird since he's the only person I talk to on Snapchat, but he says it's just the main platform he uses to talk to people. I've seen him open and reply to these and it's genuinely just like pictures of the side of someone's head saying stuff like "how are you", and he's told me who they are if I ask (all just causal friends) so it's not necessarily like he's hiding anything from me or there's anything to be concerned about, I just can't shake this off feeling I have about it. In all fairness he has offered in the past to stop communicating on there but I'd feel like I'm being controlling if I actually ask him to, I was more hoping he'd just want to change platforms knowing that I'm a bit uncomfortable with it. I do genuinely believe he wouldn't do anything to hurt me, and between his job and our relationship I don't think he even has time to cheat so I really don't believe anything inappropriate is happening. I just feel weird about it.

Would anyone else be uncomfortable with this or am I overreacting?