How do I even deal with this... please help

My bf who I live with was looking at his ex gfs pictures that are saved on his gmail of a pic of just her face and a pic of her nude double D’s. These were saved in his gmail personal folder from 2015. Yep I simply tapped on his phone and saw it open.

Just yesterday he was telling me he doesn’t need anything or anyone else because he loves me and wants to be with me forever. He hasn’t had sex with me for a week (not unusual) and I see this. He’s 33 not a teenager btw. We’ve been together 3 years.

Obviously I will bring it up to him... but I don’t know how to handle it?