Last name

I got married 3 months ago and still haven't changed my last name. It hurt my husbands feelings but I have a 3 year old from a previous relationship who has my last name. I just don't want him to feel different when we have more kids especially since his real dad isn't involved. And I do not want to change his name. My concern is that we are ttc and I have thought about the next child's last name. Should I give that baby his last name or mine or do I have to give it his name? I told my husband to change his name and he won't bc he has 2 kids from a previous marriage.