Should I be concerned my wife is cheating?

Anonymous
Long story short my wife is in nursing school. She has a study group she spends a lot of time with. They go out every now and then for drinks. There’s this guys in her group. I’ve watched them interact and they seem almost a little too comfortable for my liking. They joke around and laugh quite a bit. I don't know if it’s just me in my head at this point. The study group was supposed to go out together recently and everyone but my wife and the dude cancelled. She said she felt bad because he was ready so she went anyways. I found out by going through her phone. When I asked her about it she said she didn’t think it was a big deal and was annoyed that I didn’t trust her and went behind her back. You hear stories of people cheating in nursing school so that plays in my head. I know how academically rigorous nursing school can be so I haven’t really said anything else. What do you guys think?
Should I be concerned my wife is cheating?
29 Opinion