Dear Amy:

I don't trust my husband anymore.

We had 17 wonderful, fun and happy years of marriage. We have four children. I never had reason to doubt his fidelity and total honesty until about a year ago, when I sensed some deceit.

Then I caught him lying about using Internet porn and having a secret bank account. Now I'm afraid that everything he says is questionable.

He has been traveling for his job for the last 10 years. Trust has been the glue in our marriage.

His cell phone activity is over the top, and I can't identify most of the numbers. I found some other convincing evidence (makeup on his clothes, sending flowers to someone) that he has been cheating.

I even asked him to take a lie-detector test, and he failed.

Still, he staunchly insists that he is innocent of any infidelity. He has agreed to individual and couples counseling and has been trying hard to do everything I request to put our marriage back on track. He even switched territories to reduce his travel.

How can I know if he can be the trustworthy man I married or if he has morphed into a hopeless liar and cheater whom I'd be better off without?

- Worried Wife

Dear Wife: My favorite book about infidelity is Not Just Friends: Rebuilding Trust and Recovering Your Sanity After Infidelity, by Shirley Glass and Jean Coppack Staeheli (2004, Free Press). The authors opened my eyes to the roles that trust and transparency play in recovering from infidelity. For your relationship to heal, they write, your husband should be willing to be completely truthful and transparent in every way for exactly as long as you need him to be. Denial is not transparency.

Your counselor should be helping the two of you to negotiate terms so that you can save your relationship.