Work won’t give me part time

My work won’t give me part time no matter how many times I’ve asked. They always tell me they will talk to the boss or that I applied for full time so I need to work full time. I’m currently 36 weeks pregnant so sitting for 8 hours a day with only a 30 Min break is making me uncomfortable. All I ay least wanted was part time until I have the baby and after I can go back to full time. Also, my supervisor just told me a couple days ago that he can tell I’m stressed because my work has been slipping and basically called me lazy. My baby is growing bigger then she’s supposed to and Monday I have an ultrasound to see how big she is and if I need a c section soon so obviously my mind isn’t on work at the moment. He also told me that since I’m about to become a mom I need to work harder and was telling me since I’m about to go on leave that I need to work more to make me financially stable. Um he dosnt know if I have money saved up? He dosnt know anything about my life other then what I choose to tell him. I could go on an on about what all he talked to me about but he got to personal before knowing anything. I obviously can’t change jobs because nobody is going to hire me this far along but I don’t know if I should quit and find a part time job when I’m on leave or just stick it out with this job?