What do i do to get the correct amount for the child support that I'm supposed to pay?

There isn't an judgment for custody of my daughter. She stays with me at least 4-5 days out of the week. Sometimes that includes overnights on the weekends. I pay 17% in child support to her mother as per NY law. I calculated this myself. There is no child support order. I want everything to be official and I want the correct amount to pay.