Just want some advice !

So I’m currently 38 weeks. at first before I was pregnant my MIL and the rest genuinely loved me and what how good I was to my SO. Now I feel like I’m just a incubator for their grandchild. Here’s why. So my MIL doesn’t work. So my SO feels that we don’t need to pay for a babysitter because she is free. But I’m not sure how reliable she is. She takes medicine for a bipolar schizophrenic disorder and when she’s on her medicine she’s fine. I believe she would be able to take care of my son. But if she doesn’t take her medicine or can’t afford it (which them not being able to afford things happens often. Due to her overspending.) I’m nervous to as what would happen if she couldn’t get him to calm down. Or if she had a break down. I’m not saying she’d hurt him or anything but I want to know she’d be able to handle it. Anyway. I’m just sorta uneasy about it. I’d love for her to be able to spend time with him. But not so much that she thinks he’s her and raising him. Which I feel like she’s gonna try to do. However she’s told me before I need to have a back up everyday just in case she doesn’t feel up to watching him. Today I was telling her my doctor recommended me more time off to my job. And not just 6 weeks. And she had the audacity to ask ME. If I was going take her time with him away from her. I simply told her you’ll get him when I go back to work. If I go back at 6 weeks you’ll get him then if not. You’ll get him when I decide. This is why I feel as if I’m just an incubator to them. Her statement really bothered me. And if I say anything she’ll blow it out of proportion and make me seem like the bad guy. I’m sorry but I don’t even think 6 weeks is enough time with my baby. I want him to know he’s my son and I want that bond with him. She just seemed so eager for me to go back to work so she could have him and I haven’t even had him yet. He’d be with her everyday 6:30 to 5:30. I’m scared he won’t know me. I just feel like she feels she has a right to him. And I feel like being anyone other than the parent of a child is a privilege. Anyone ever been in a situation like this. I don’t even wanna leave my baby that long. I didn’t really want him being anywhere other than our own home at that young. I’m just at a loss.