Men are still cheating more than women (although women are catching up, say experts). Not even newlyweds, who should still be in the honeymoon phase, are immune to infidelity. Many people in their first year of marriage call Raymond C. Ranno, a private investigator running R.C. Ranno Investigative Services LLC in Middletown, Conn., says Ranno, to investigate their new husbands and wives. "It's easier to get divorced than it is to get married nowadays," he says.

"The oath meant something more before."

Suspecting your husband of cheating, whether you've been married a day or 50 years, is like being stuck in a nightmare from which you cannot wake. Accusing your spouse of infidelity without any proof can destroy your marriage because it shows a lack of trust. But not paying attention to warning signs is a mistake, too.

"Marriage is a difficult thing, and I never cease to be amazed by the type of person who commits infidelity," says Ranno. "They take the risk of ruining good lives for the opportunity to have sex once or develop a relationship on the side."

If there's any hope of saving your marriage (not to mention yourself), you need to know whether an affair is actually happening, says Janis Abrahms Spring, a clinical psychologist in private practice in Westport, Conn. And author of After the Affair: Healing the Pain and Rebuilding Trust When a Partner Has Been Unfaithful (Harper Paperbacks, 1997). "You can always hire a private investigator. I suggest doing it," she says.

"People need the truth."

Whether you choose to hire a private investigator is up to you. Remember that if your husband is being faithful, and he discovers you didn't trust him, you'll be putting your marriage at risk then, too. Before you let paranoia get the best of you check for some of the other warning signs that he might be cheating. Here are the warning signs that your husband is cheating

1. Secret Behavior with Cell Phones and Computers

Your husband once was an open book. He told you everything, even to whom he said hello at the supermarket. Now, he's holding back. He is shutting off his cell phone or putting it on vibrate and taking calls in the bathroom with the door closed. He shuts down his computer when you walk in the room or he keeps it locked from prying eyes with passwords. He might be keeping a hidden e-mail account, says Ranno. Maybe he gets calls at strange hours, says Mark Chauppetta, a private investigator running On the Mark Investigations, which is based in Brockton, Mass. Funny things could be happening on your husband's Facebook page. A spouse with something to hide can't be trusted.