I'm going to cheat on my bf at 9 months pregnant...

My boyfriend and I have not been getting along at all the last few weeks. A lot of it has to do with all the stress we're under, bad communication and my hormones don't help either. We had a pretty big fight yesterday and eventually we calmed down and really talked. Things seemed to be going in a good direction. We went out for ice cream and treated each other a lot better all day. Until dinner time, I'm putting away dishes and when I'm done I walk into the bedroom where he throws my phone down and gives me a dirty look. Apparently while I was cleaning up he went through my phone. Which really upsets me, not that I have anything to hide that's just my space and shows he really doesn't trust me. It hurts. Well out of everything in my phone he finds ONE thing he doesn't like. A few weeks ago an old fling added me on snapchat, I am totally willing to admit I was in the wrong when it comes to accepting him and on top of that not telling my boyfriend. But in all honesty it barely crossed my mind. I'm so busy thinking about this baby, that is due in less than two weeks! It's like everything with us was finally okay and he had to go dig around to find something to fight about. I'm exhausted trying to maintain this relationship when all I really just want to focus on the life I'm about to bring into this world! And really, am I really going to sneak around with another man at 9 months pregnant? How stupid is that?