is this possible?

Arianna • With the love of my life and mother to our handsome little boy ❤️
Hey ladies. Okay so my fiancée and I have a 11 month old son. Things used to be great but lately I highly doubt we will stay together. When my son was born I put my fiancée on the birth certificate and gave him his last name because I really thought we would get married and be together forever. Well things are going horrible lately. If we break up, I want my son to have MY last name. Is there a way to do that?? Is that possible? What do I need to do? Also can I take my fiancée off his birth certificate? He is telling me that if anything happens he's going to try and take my son away from me, and if I was to take my son to go visit my dad (he works out of town) that he would call the cops that I kid napped him. Is it possible for me to change my sons last name to mine and take his father off the birth certificate? If so, how do I do that? I know things aren't going to last and I wanna be prepared to do whatever I can. Thank you!