Should i be worried?

So I get my boyfriends phone and look through his pictures ( he let's me when I'm bored ) and I'm scrolling and everything he's across the class talking to his friend about some shit and I come across screenshots of a conversation between him and his ex ( the one before me ) now that hijo de puta cheated on my boyfriend while we were friends and I was the one telling him everything was going to be okay. Next thing you know couple months later we're together she's out of his life and I'm all happy then I find out that they still talk like as if nothing happened. I told him he said he'd stop talking to her I said okay then I find out it happens again and I get upset. A few months later he goes to his best friends house and invites me to go but I didn't feel like it next thing you know I find out that that bitch is there. With him. I go and I text him telling him what she's doing there and he says that they're just friends. And after I read that I felt a sick to my stomach. Next day I tell him in person " you can forgive her for what she did to you but I'm not comfortable with her being all over you and you being friends with her I don't care if you trust her I don't so just leave her alone " and he agreed so these screenshots I see are of her texting him saying how she's depressed because she doesn't know why he doesn't love her anymore and how she misses him and bull crap and all he writes back is "OK" and it just bothers cause he doesn't mention me at all. I would've been fine if he ignored it completely or at least tell me that she texted him but he didn't and I'm here worried if he's just going to forget what I said and go back to her.