Dating apps?

Me and my boyfriend have been together for a year now, last night my mom (who hasn't gotten along with my boyfriend) contacted me saying she and some friends had found my bf on a dating app... Granted that's where me and him had met and I thought maybe he didn't delete his account? But then they said it was a recant picture of him... I got very upset and asked him about it he said he has never been on it after we got together and had deleted all the dating apps. Now I'm not a girl that  looks through his phone or stalks his facebook page or reads through his texts, but last night when I found that out I needed actual proof that he wasn't on there like he says, so I asked him and he was fine letting me go through it. I didn't find any evidence but now I feel like a bad girlfriend... He was caught having a sexual converstaion with his ex around the 2nd month we were together but other then that he hasn't done it again and we got through that situation. Any advice? Should I have done what I had done? Was it bad I went through his stuff?