“Many times, the cheating partner can start to become overly sensitive over his/her non-shared personal items such as their phone, car, or living space,” Lauren Peacock, relationship expert and author of Female. Likes Cheese. Comes with Dog.: Stories About Divorce, Dating, and Saying “I Do, tells Woman’s Day. “For example, if before he/she left their phone out while taking a shower, they may start to bring it into the bathroom with them or become very agitated when their significant other asks to look at a funny video or something else on the phone.” That kind of possessiveness can signal that they’re actively hiding something — or someone.