Help should I be concerned ??

So I’ve been with my bf for a year and a half, and his previous relationship he was in lasted 4 years. He’s told me that she was very controlling amongst a lot of other things. The other day I had got on his phone on Snapchat because I wanted to take a picture of something on my Snapchat without that person knowing I screenshot it. So when I went to send it to myself on his best friends list was a name of a girl I’ve never heard or seen (I don’t care if he talks to girls I fully trust him and he’s not one to cheat) so I just asked who it was and he said oh just a girl from hs she was talking about something on my story and I just said okay. And then I sent that snap to myself and noticed her name wasn’t on any of the people he had recently snapped so I scrolled a little bit and never saw her name so of course I got upset because he obviously had deleted the messages. Another situation like this has happened and he just explains that in his past relationship that’s what he did because his ex would freak out but the last time this happened I told him it’s much better if he leaves it and I won’t worry about it. He doesn’t understand that it makes me think that there’s something he doesn’t want me to see. Am I overreacting or should I be concerned ?