mom treating my newborn like its hers

Your mother needs to remember whose child this is.

You may need to appeal to authority, e. g. tell her that you're doing such and such because your pediatrician said to. It's hard to argue with the expert.

Can I ask how old you and your mother are? And the baby? You're just going to have to be firm with her and tell her she had her chance to raise her own kids and now it's your turn.

im 21 and my mother is 49 my daughter is 4 weeks old

Are you planning to move back to your own place soon? I'm a grandmother and I have to bite my lip, but since its your Mom, don't let her take the baby like a party favor especially if she says you don't know what you're doing. My parents offered their home for me to recuperate, I thought I would stay about 2 weeks, but my nerves were shot after 4-5 days so I went back to my apartment. It's hard, but not a total morale buster. I have a few other suggestions, but I'll give the rest of the crew chime in. I'll get back later. Good luck!