If you both cross a line, does it cross each other out?

JoAnne
I just started dating this guy. We have a lot of fun together and we have great sex, but I've probably argued/gotten mad at him more than anyone else I've been with. Did I mention awesome sex? Oh yeah. Anyway I felt like he was acting fishy so I went through his phone. I'm not proud of this, but I found him sending nudes to a girl he works with. I kind of want to break up with him because I don't want to be in a relationship with someone who thinks it's okay to do that. But technically he didn't cheat. And the only way I know this is because I violated his privacy. 
What should I do?