Please help me Give my son my last name!

My ex-fiance is having my baby and will not give the baby my last name. She knows how important it is to me and how I feel about it but she still will not give my first son my last name.

I remember reading somewhere that if my name is on the birth certificate as the father and I petition the court to make her give my baby my last name she doesn’t have to comply but when the baby is born and I enter another petition to the court to make her give my son my last name then she would have to comply because she did not comply the first time.

I was just wondering if this was true and if it is where could I find that information. Pleas Help Me give my first and only son my last name!