The only two ways you can know for sure if your girlfriend is cheating on you or not is by communication first. Sit down with her; face her and ask her right out if she is cheating on you. If she goes red in the face; fidgets with her hands or squirms around; stands up and threatens to leave or go into another room it is highly possible you have cornered her into confessing whether she is cheating or not. However, if you have no real proof she is cheating on you and she may not be then you risk losing her. Secondly, when she is away from you and when you think she has the opportunity to cheat on you then you can follow her one evening.
