<human>: Condense the text into a few key points

My  boyfriend  and I have been together two years. In that time we've been through a lot including a major move to a large city. Everything was pretty fine.

We wanted to add a little more to our sex lives so we brought a couple people into our bed. It happened on three separate occasions and for the most part was fun. Also, a few months prior to this the boyfriend comes out as bisexual. Okay, bit of a shock but he loves me so we talk about it and that's that.

About a month ago I was using his phone and noticed some peculiar things, so I snooped (oh well, I'll be that asshole) through his email and saw message after message from him and random dudes on craigslist. All about meeting up and fucking. All guys. He even posted his own ad about 2 months prior that was quite explicit.

All of these messages included nude photos of him and messages that mentioned him being in a straight relationship so it had to be discreet. I did some more searching and found  out he masturbated on Skype with some random guy.

I was so angry and hurt I couldn't even talk to him. I wrote him a letter and left the house. He called and we talked. He explained himself and said he never met up with any of them (which I believe, we share a car) and that it was mostly for attention. I'm sure to most people staying with the guy sounds extremely dumb. 

I'm not sure if I made the right choice though. I question if he's just gay and can't admit it, or if when he's up late he's doing those things again. He gave me access to his phone but everything can be deleted.

The only saving grace here is that he's always willing to talk to me about it and since then things between us have been pretty good. I just can't shake the anxiety and fear though. Could there be any resolution to this? I love him through all his shitty faults but this happening has set me on an anxious roller coaster ride.
<bot>: boyfriend came out as bi. Found explicit messages between him and guys from craigslist as well as Skype. Having major anxiety about staying and trusting him.