Boyfriend help

I don't post much or ask for help a lot but I've been pretty upset lately. I've been with my boyfriend for over a year and a half and we've been through hell in back he was there with my through a miscarriage 2 job losses and so much more but the other day I found nude pictures of other girls on his phone that he screenshotted off of Snapchat. I love him to death and I don't want to break up with him but I do what to talk to him about it but I just don't know how to bring it up. Any suggestions?.... I seriously can't focus on anything else. I just keep asking myself if I'm good enough and if I do enough to make him feel wanted or why he feels the need to get pictures from other girls. Please help!