Last name for my baby? Please help!

So... I’m about to be 28 weeks pregnant & my daughters father hasn’t been around.. bought her anything.. checked on her.. nothing. I’ve been reading around that dads last name is earned.. which I totally agree. But he hasn’t earned it at all.. I don’t think he cares for her. It hurts my feelings but it’s alright cs babygirl will always have me💓 but I’m going to be changing my last name soon.. idec to what. But it won’t be what it is now. So those are 2 last names out the window.. then there’s my mom.. I was going to give her her last name but my mom just found out that her dad isn’t her real dad.. so she is going through the midst of trying to see who her real family is.. I have a stepdad who has been in our lives for 10+ years... I want to ask him can I give my baby his last name but I’m scared.. I was going to look on google for last names for my baby☹️ Ik that’s so sucky but idk what else to do ! I just don’t want to go through with that & she hates me for it when she gets older.. what should I do?