Should I tell him?!?

So basically my boyfriend fell asleep next to me and I went on his phone to change his wallpaper to a picture of us, because it’s a brand new phone and I thought it’d be a nice surprise to see when he wakes up... so I’m scrolling through his photos trying to find the best one of both of us, when I find a picture of him and his ex girlfriend cuddling and smiling. He told me he deleted every single one of them and that I wouldn’t come across another photo of them again as it’s happened in the past.... I feel like absolute shit, I want to go for a walk but it’s dark and I’m pregnant so I’d rather not be alone but I don’t know what to do? Should I speak to him about it or ignore it? It’s really upset me and affected me but I don’t want us to fall out about it 😕