Sounds rough, its a shame its all based on sex. Have you guys ever thought of seeing a proffessional about your situation. Has it always been the same. Does he spend time with the kids and do the dad thing, help them into their transition toward adulthood. Does he romance you at all, it seems he's a big kid that needs mothering, and avoids the emotional contact. I have been married over ten years, two young kids and next to no sex life. I see things from my wifes perspective and accept it. I do what I can because it aint all about me. Being a dad is the number one focus as well as a supportive husband, the rest will happen sooner or later. Caring for kids is bloody hard especially 5 of them. Perhaps call his bluff maybe he may appreciate what he had once its gone. Get some help drag his butt to counseling or he can pack his bags. Time for him to grow up be a man. Good Luck