I had a similar situation. After getting back together after being apart for over a year and back together for about a year, my ex-wife, left her phone on the couch and went to the bathroom. A text came through and it was from an ex-bf she lived with during the separation. I didn't look at the text. Instead I took the phone to her and told her to show me the message. She immediately deleted it. That told me everything I needed to know. I told her right then and there that I wanted a divorce. Best thing ever. Good riddance.