Is he cheating?

So I know I shouldn't go thru my boyfriends phone but I did and the last two times I did I found him emailing and texting some girls on Craigslist. I'm so scared to confront him! I know I was wrong for going thru his phone but now I'm not sure if he's cheating on me. He says he has never and wouldn't ever cheat on me but it looks like he's trying to hook up with these girls and now I don't even know who he really is. I'm so confused and hurt. What do u think? What would u do?