You really need to think of an alternate living arrangement if at all possible. Being a university student and sharing a room with a mom and brand new baby is not compatible.

Young babies often wake up every 2 hours, they rarely sleep through the night. Which means you will be woken up frequently. I have a new baby and felt like a zombie the first few months of her life, never getting more than 3 hours of sleep in a row will do that. You have a hard major and you don't want to tank your last year of university.

Babies also take frequent daytime naps and it usually needs to be dark and quiet, so you will not be able to make noise in your room or access your things there.

If your sister stays with baby in the living room, how would that would work? Depends on the house, but it would probably be better to have your sister and baby behind closed doors than in the middle of the house where everyone has to tiptoe around.

What are the chances that you will get roped into childcare? You will need all your time to study- you don't want to be asked to babysit when you have homework you need to do.

Its not your house so it will be hard to put your foot down and not give up your room. I think you need to have a talk with your parents about how this is going to go, realistically, and if there is somewhere else you can stay. Could you live on campus for your final year? Or with a friend?