Infidelity puts a strain on any relationship, leaving you reeling from the emotions that come along with discovering a cheating husband. Learning that your husband has been cheating with one of your friends provides a double dose of pain, leaving you to wonder who you can trust. There are several signs to look for if you suspect that your friend and husband are engaged in an affair.

Examine your husband's cell phone bill. According to an interview on MSN.com, higher cell phone bills linked to calls to your friend's number indicate that there is more than just a casual conversation occurring. If you have access to your friend's bill as well, check hers to see how many times she has called your husband.

Check all bank accounts that you and your husband hold. Cheating men spend more money to romance their new affair. Keep a record of any flowers, candy and expensive gifts that your friend receives and cannot account for.

Note any grooming habit changes in both your friend and husband. Frequent showering, new fragrances and undergarment purchases not explained by normal wear may be signs of an affair.

Time absences that last longer than normal. Trips to the grocery store or fast food restaurants should not take one to two hours. If you notice frequent absences of your husband and friend at the same time, then you should start suspecting something else is going on.

Watch your friend and husband when they are around each other. Notice if they act secretive. Also take note of whether your friend shows some hostility toward you. Taking the time to pay attention to these behaviors will give you helpful insight.