Is he thinking about cheating?

3. He calls you crazy or depressed. "When he starts acting suspiciously later, staying out late, you'll question your own suspicions," says Landers. "After all, he told you that you're crazy -- you'll start to wonder if you are."

4. He starts doing strange things with money. Money or bank statements are suddenly missing, he's carrying around lots of cash or he's spending too little cash. "He could be trying to get money together for when he eventually leaves," says Landers. "Or he could be trying to cover his tracks, or not spending money because he's staying in with his mistress to avoid being seen." Any behaviour related to money that is out of the ordinary can be considered a warning sign.

5. He buys you big, expensive gifts. "You'll think, how could he cheat on me when he bought me this big diamond?" says Landers. "But it's more likely he bought the gift to throw you off or to hide his own guilt."

Knowing the telltale behaviour is a way to arm yourself against betrayal, says Landers. "When he starts acting out parts of the script, you need to take action," she says. "If you think something is wrong, it probably is. Don't make excuses and take action. A doctor would say to treat the pain early before it gets really bad. Our natural instinct is to let it go, not make trouble, but you need to do something."

Landers suggests getting counselling together or, if he refuses, go alone. Find a resource or facility that can help you, whether it be a psychiatrist, a support group or your church. If you don't have help available, Landers advises keeping a journal and writing down any suspicious occurrence. "It will help you assess the situation," she says. "You can interrupt the script by not going along with it. Don't allow him to convince you to doubt yourself."