My boyfriend was going to cheat?! What do i do...

Hi so I'm 18 and I have my boyfriend of almost 3 years. We have a beautiful son I just recently had a month ago.

I felt like my bf was different so I made a fake Instagram account and talk to him. The picture below are what we talked about. The last three messages are after I called him and told him it was me. I broke up with him but idk we have son..

Need advice! I want to hear it all. Bad good and silly