My daughter is not the biological factor of my former husband, although we were married at the time she was conceived and born and for three years after that. He continued to have visitation, paid child support, provided health insurance and claimed her on his taxes. She is now seven years old, and he has decided he doesn't have to pay for her any more. My lawyer says there is a good chance he does have to pay because he is the only father she has known -- and something about equitable estoppel. What to do?