I pay through the CSA and see my daughter every week, my ex has married and has two children with her new husband, how can I put my last name on my child's birth certificate legally, she does have the paper work but refusing to sign, or saying I will think about it, help Chris

Whether you are on the BC is not up to her, assuming you weren't married when the child was born. Contact the vital statistics office for the state where the child was born about how to submit an affidavit of paternity and get yourself put on the BC (assuming there is no question but that you are the father).

Is your visit with your daughter though court ordered visitation. Is there a child custody order in place. Have you been determined to be the father in court by statement of paternity or by DNA test?