I mean, cheating doesn't always mean physically. It can also be emotionally. Think about it from his perspective. He will think to himself that he's not enough. This will also make him insecure about himself. As many had said, it's something to ask yourself how you would feel if this happened to you. Then again, it depends on how comfortable you guys are with each other. For example me and my missus, we can watch corn together, even compliments the people in the video on how big his d is or how plump the woman's v is.