A little worried.

Okay so a few months back we'll more like in January my fiancé had downloaded a online chat thing and when I went through his phone I had found nude pictures and a few videos. I lost it I cried so hard because I never thought he would do something like this. Well we are together still but I'm always still worried it'll happen again. I know it's bad to think that because I should be able to trust him but what should I do? Should I just talk to him about how I am feeling or should I just ignore it? Someone give me some really good advice because I'm still super bothered by it all.