Help Me, New Mom in Need!!!!

So im new to all this Mother hood stuff and im only 16 but my support system is great but i just need some advice because the babys father is my boyfriend and my boyfriends mother is a little over bearing you know?! she’s acting like the baby is hers and i feel like i should be doing what she tries to do. 🤦🏽‍♀️like plan the baby shower i want to do that but i just don’t know how to tell her to back off, HELP ME!!!!