Lately, when I've been talking with readers about their marriages and long-term relationships, I hear the same question over and over. "How do I say I'm not satisfied with our sex life?"

Some say they are unhappy because they have little or no sex in their marriage. Others wish they could find the nerve to tell a partner about sexual fantasies or what they really want to do in bed. Most worry their spouse doesn't notice there is a problem and that they feel unfulfilled.

You'd...