Hi Magnolia, so how long did you live with your husband's parents for? Have they moved into another house and you rent from them, in their previous house? I'm trying to understand the living situation.

Why do they stay for up to 3 weeks with you and your husband? Does your MIL help you care for your new baby? Is the issue that you feel like you lose your power when they visit, because you're still in your husband's childhood home and not really your own home?

Have you directly asked your in-laws not to stay with you for 3 weeks, or does your husband override your need for space, and invites his parents over for weeks at a time to visit? When you write that you've tried talking to your inlaws "to no avail" what do you mean, exactly? That they simply refuse to listen to you? Can you be more specific?

Grad school is online, correct? Can you create a calendar to post in your home's kitchen of your study time, time to spend with your child, time you are at work, etc., so that your husband knows where you are and what commitments you have?

I think this is an issue about communication and communication breakdown.

You need to find a way to compromise with your husband and inlaws so that everyone feels like their needs (including yours) are met.

What have you communicated to your husband and inlaws to make sure yours, and their needs are met? And why has that attempt failed?