Boyfriend issues

My boyfriend decided to download VSCO a while ago and it was all good and then I noticed his favorite were all have naked girls. Vsco isn’t like tik tok where it’s just random people instead it’s typically people you know. It bothered me… He deleted the app eventually because it really hurt me. It’s has been a couple of months and he gave me his phone when he was drunk and I noticed a notification. A vsco notification. So I decided to look (just like I think any other human would) and I found the same thing he was doing before. I brought it up to him and he has no explanation. He said “I don’t know” no matter what I asked him. I cried for a while and now I don’t know what to do. I obviously can’t trust him on his phone. Worst part is we’re at the age where he should grow up. I know the saying is “men never grow up” but men shouldn’t do this… it feels like cheating to me in a way. I really don’t feel pretty either because I don’t look like them.