Legally changing last name

Lindsay • Enjoying every second of our beautiful baby girl
So my boyfriend and I have been together for quite a while now and we are expecting a baby in June. We both want to get married eventually, but this baby was not planned and both agree that we shouldn't rush into marriage just because of the baby. I want the baby to have his last name because I just do, but it bothers me that I will have a different last name. I was thinking about possibly legally changing my last name to his. I haven't done any research on this yet so I'm not sure what it entails or if it's even possible but just wanted some opinions?
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Apparently I wasn't as clear as I thought when I said "we both want to get married eventually." It's just not a good time for a number of reasons. It has nothing to do with me not being sure or not wanting to commit. And the reason I want to change my last name is so it would be the same as my daughters in the mean time.