If you haven’t defined your relationship as exclusive, have that discussion because the behavior you are concerned about might not be cheating to your dating partner. Ask your boyfriend if he thinks you have an exclusive relationship or if you are both free to see other people. If you feel you are exclusive and he doesn’t, then ask him how he sees the relationship and where he thinks it’s going. If you can’t agree on the status of the relationship, he probably doesn’t think he has done anything wrong or that he has cheated. You may ultimately decide the relationship isn’t worth saving.

When both of you want to maintain the relationship and are willing to agree that it is exclusive, you can talk about the boundaries you want to set. Women often feel more strongly in defining specific activities as cheating, according to a 2013 study published in Evolutionary Psychology titled “Was That Cheating? Perceptions Vary by Sex, Attachment Anxiety, and Behavior.” You might decide that having sex with someone other than your dating partner, being emotionally involved with someone else and petting or having oral sex constitutes cheating, but flirting, kissing and holding hands are acceptable. Whatever you define together as cheating, make a commitment to stay within those boundaries.

Now that you know where you stand and what constitutes cheating, you can establish trust based on how you expect your partner to behave. If your dating partner steps over the boundaries you set together, then it is time to assess how healthy the relationship is because your trust has now been broken. Sometimes a dating partner will cheat to end the relationship, advises Lonnie Barbach, author of "Going the Distance: Finding and Keeping Lifelong Love." Dating partners who try to maintain the dating relationship and cheat are more likely to cheat in a marriage, according to Barbach.

If your dating partner cheats after you have agreed that you are exclusive, it is time to decide whether the relationship can survive the betrayal you feel, says Mira Kirshenbaum, author of "Too Good to Leave, Too Bad to Stay." To save the relationship, your dating partner must admit that what she did was wrong, take full responsibility for the behavior, end the affair and work with you to determine why she cheated. Further steps include deciding what actions the betraying partner must take to prove remorse, restore trust, reconnect with you and maintain accountability. If these steps can’t be met, you are probably better off ending the relationship.