Birth certificate question hope someone can help me!

Hello everyone! 
So I have two questions regarding to "birth certificates" and I'm looking to get help from here since I don't have anyone much to ask. 😓
I have a 1 month old and I want to change his last names because while I was in the hospital I was in a lot of meds that my parents took over and they literally just made their own choices and because I was in strong meds I was so unsure of what to do that I just went a long with what they had decided. Now that I know better I am unhappy with my baby's last names and I want to change them. The baby's father unfortunately is not with us anymore in this world so he will never be involved. 
But what can I do to change his last name on his birth certificate?! Please help me with this! 🙏🏻
Also, all my life I've had problems with my whole name as well because my mom didn't really know and she put her last name included with my name and middle name so I would like to correct this and put her last name as my last name since I only have my fathers but we've never had a good relationship at all so I rather have my moms first. And I'm 25 by the way. 
What can I do for this situation?
TY in advance for those who comment ❤️