Boss is going to make me go into labor!

I'm a part time employee but for the next couple weeks my boss has me working full time hours. I usually either work all day for three days or half a day for five days but now my schedule is 8-9 hours five days a week. I'm 38 weeks and I am so worried that I will go into labor at work and my boss won't have a backup to take my place. My job isn't like some jobs were there are several people on the floor that can take over if someone can't make it. My job is to answer the phone and run the mail and I am the ONLY one in the office that does that specific job. The other 4 employees that are under my boss are all trained to do what I do but all of them say they don't remember how and they are all scattered around the building doing other jobs that only they can do so it would be difficult for them to fill in for me anyway. Last Friday I got a note from my doctor saying that I needed to stay home and rest for that day because I had a terrible yeast infection that made it painful to even sit down. The only thing that made the pain go away was lying down with an ice pack in between my legs. When I told my boss I couldn't make it she sounded so frustrated and acted like it was going to be hard to find someone to fill in for me. This makes me mad because it's not like she doesn't know I'm 9 months pregnant and could go into labor any day now. I figured that after last Friday she would at least put someone on the schedule that could take over if needed but nope, she didn't. I'm moving out of state in February anyway so sometime today I am just going to have to tel her that if I haven't had the baby by next Friday then that'll be my last day and I won't be coming back.