Should i be suspcious of my bf?

Ok so here's the situation. I have been talking to this guy for almost a year and its starting to get serious. The other night when he was asleep i went through his phone and in his saved pictures there were twoseparatee pictures of two different men with their shirts off. One way standing up and one was like reclining on the couch. I have been so uncomfortable the past couple days since i saw the pics. I dont know what to think! Im nervous to confont him because then i would have to admit to going trough his phone...