Boyfriend advice :(

So yesterday I found out that my boyfriend has a lot of nudes from his ex girlfriend and many many others that his friend sent him hidden on this app. They are all from a really long time ago like before we started dating and I know that for sure but he still has them. He said he didn't delete the app because it didn't work and he couldn't login but idk if I can trust him because he still had it on his phone! I love him so much and I don't want to break up but i feel like I need to because I'm not the kind of person that lets people just get by with stuff like this. I've never been in a situation like this I need some advice. Me and him have talked about it a lot and he says he's really sorry and all that but idk if he's lying because I feel like I can't trust him SOS :(((