Kelley Keehn is an expert in money psychology and contributor to On the Money. Learn more at KelleyKeehn.com

You suspect your spouse is cheating but you're not sure. To make matters more complicated, the likely lover is money. Spending and hiding debt behind your back can be as much of a betrayal as marital infidelity.

Here are some red flags to watch out for if you suspect your spouse is having a financial affair:

1. A change in calls. Whether it's a bill collector, lawyer or a financial company that your spouse then shrugs off as a wrong number can be a telltale sign that something's awry.

2. Watch your mail carefully. Have you discovered new companies mailing to your spouse or the household that you haven't seen before? What about regular mailings from your lenders that have mysteriously stopped, signifying that your spouse might be rerouting them to work or a post office box?

3. Monitor your accounts. Keep a close eye on your bank and investment accounts. Be on the lookout for suspicious withdrawals or deposits. If your spouse casually and vaguely asks you to sign any piece of paper without explaining it or allowing you to review it fully, don't do it!

4. Unusual or abnormal behavior. A spouse having a financial affair might act very similar to one having a standard affair. Are they withdrawn recently, agitated about purchases or suggesting spending more than usual? Do they disappear for periods of time or shut there cell phone off and make themselves unavailable without explanation?

Unfortunately, financial secrets feel very much like a betrayal to the one being left in the dark. Empower yourself to take charge and monitor your family finances if you suspect less than normal occurrences. And remember, financial secrets never, ever stay a secret for long.