While cheating men are more likely to have sex even more with their cheating partner, it's less likely for a cheating woman to react the same way. If she's getting some love somewhere else, then she may feel guilty, or just plain not interested, in sleeping with you. If you previously had a pretty good sex routine going, and now she's been "too tired" or "not feeling well" the last ten times you tried to make something happen, it could be a sign that she's getting satisfied elsewhere.

• If she's cheating on you, she'll also be less open with her body. She won't want you to see her undress, and she'll be more likely to cover up in bed.
• Of course, her not wanting to have sex could just be a sign of her general dissatisfaction with the relationship, or just her unhappiness in her own life. Still, if she's flirty and fun when when she leaves the house, and completely withdrawn with you, it's a problem.