Last Name Dilemma

Aravella
I have been dating my boyfriend for about 2 yrs now we started dating right after I had my first daughter. And now I'm pregnant with my 2nd due in May, but we are constantly arguing over the baby's last name. Since we are not married and my 1st child has my last name I want my 2nd to have my last name as well. He says if I don't give the baby his last name he doesn't want anything to do with me or the baby. I think that's completely ridiculous, we don't even know what the sex of the baby is and he wants to argue about this not even compromise with me. Ugh what should I do??