Name game=Heartbreak hotel

I am 37yo and 34 weeks with my 3rd child (2nd son) and have argued about a name for the last few mos. My oldest is from a previous relationship. My son and this baby are with my SO. He refused to sign the birth certificate and distanced himself after my son was born because I didn't want him to be a Jr. Well, here we are again and I still don't want a Jr. He has asked if I want to be miserable and unhappy. He has attended 1 appt and stayed in the lobby and has not paid for 1 visit. Am I being unreasonable or selfish? I don't want my son living under someone else's name, not even his father's. My son has my last name and he often brings that up but in La unless the father signs the birth certificate, the baby takes the mother's name. He chose not to. Help?!