Did he cheat?

I think I caught my boyfriend of almost 3 years cheating. I noticed on his phone that he had gotten an email from Craigslist. Normally I would've left it alone but this time I had a gut feeling that something wasn't right so I check it out. Turns out it was some girl messaging him back. She posted an ad saying she was "looking for a good time" my boyfriend responded to it saying "what's your number" and she messaged back saying " I'm going to want to know your wants and needs before I give that out". That was all there was to their conversation. I confronted my boyfriend about it and he said he didn't actually cheat because they didn't actually do anything. I know I can't trust him anymore. I just don't know what to do!

UPDATE: I just found his dating profile. I'm officially moving out tomorrow!