<human>: I have had trust issues my whole life and a history of cheating girlfriends hasn't helped it. My current SO and I have been wonderful with only one incident about a year ago that even registered on my distrust-o-meter and it was only a minor setback in our relationship. 

Recently I've been having troubles sleeping and in a stupor of stupidity, boredom and sleepiness I fucked up and did a quick snoop. Low and behold, pretty much immediately I found a chat log between (Let's call her Lisa) Lisa and her ex wherein she sent a nude picture, alluded to recent sexual encounters and tried to plan a future encounter. 

I don't want to break up with her, despite this I still love her. Big question is, how do I fix this flat tire on my motorcycle without making it a unicycle.

Can you summarize the given text in a few sentences?
<bot>: I snooped, girlfriend cheated, want to fix relationship, don't know if can. You are tearing me apart Lisa.