How can I tell if my husband is having an affair?
The fact that you are suspicious in the first place raises it's own red flag. The typical clues could be a change in how he spends his time, how he uses his cell phone, and unexplained purchases on the credit card. A decrease in love-making, a change in his over-all behavior, meaning, is he more tense, anxious or evasive. These kind of changes would invite no less than a heart-to-heart talk.
Instead of looking through his wallet, cell phone and computer history, the best thing to do if you have suspicions is to simply ask him. You can tell him of your wonderings and be open and honest with him about your feelings and concerns.
You need to give some thought to what you would do if he answers "Yes". Are you ready to end the marriage if he has been having an affair? Are you willing to work through this deep hurt with a professional counselor? Is he willing to give up the affair? Many men are relieved when the secret is over. The hiding takes alot of effort.
The important thing to remember is that most marriages can survive an affair if given the right kind of support and the spouse who is having the affair is willing to end it completely. The second most important thing is to take a look at your overall relationship. Are you two meeting each other's deepest needs? Is someone being loved starved?
Either a "yes" or "no" answer requires talking with your spouse. Secrets are not helpful in any relationship, especially marriage.