It sounds like your husband may be using sex for a sexual release rather than being truly intimate. This often happens when a couple have been together a long time. They often forget how to romance each other and simply have sex when the need is there. I have a favorite resource for this problem called Mars and Venus in the Bedroom. It addresses the differences between sex and gender but also how sex changes during a relationship. If you apply these principles you may return to a sex life that has passion. You can also introduce new techniques by getting a copy of the Joy of Sex. Sometimes the reason is not something deep and mysterious but simply a relationship that has gotten a little stale. See where he stands on new techniques or positions to bring a freshness to this situation.