Living with inlaws with baby #1

Long story short(ish)- I stuck with and supported my partner financially through severe PTSD (post traumatic stress disorder) for 2years at the age of 18. His family ended up having to help us out with money to move back home from Australia. Now we are having our first baby and we are living with his mum, dad, 2 sisters, brother in law and 4yo niece who is rather bratty and has behavioural issues, and 1yo nephew. My partner is not mentally ready to support us on his own which I fully understand, I don't want to put pressure on him. He is working full time and that's big for him. I appreciate what his family have done for us, But I am a super private and shy person and need space and quiet which I can't get in a noisy household. My SIL is already showing signs of being clingy and controlling of my unborn baby which is driving me insane already. I can see things like breastfeeding and bonding time being a challenge for me and while my partner understands, he does not completely speak up about everything. He thinks I should appreciate the help but I want and think I deserve to learn and experience this on my own. Anyone else in this position? How do I approach this nicely 😣