Most people think it's better to wait until you have proof, but I myself have been cheated on and looking back I felt it was obvious.
Men distance themselves when they know what they're doing is wrong. Many girls dont realize this factor but it's proven in mainly men. Even when cheating the man usually understands what he's doing and tries to remove the problem by distancing himself from you. Signs are also obvious like lying, missing important dates, making excuses (or always having one), or you feel a sudden lack of trust with them.
He isn't cheating on her.
you will know if your cheating when you are dating someone and dating someone else at the same time.
Justin Bieber is not cheating on her.
Try, I don't know, NOT CHEATING.
The Patriots did not cheat. Therefore they could not have known they were "cheating".
If they know about each other then no, it's not technically cheating.
Ask her if shes cheating on you! Nah im kidding i dont know sorry ? :( and im a guy
Most likely in the same ways that you might know she was cheating with a man. It could even be less obvious, though, especially if she was cheating with one of her female friends.
atitude
ask him
Follow her
Ask her.