need advice for asking for early maternity leave

So- work typically allows pregnant ladies to call in at 38 weeks. I happen to be oh so lucky where they decided to stop with me with the call in at 38 weeks and now have to work until I deliver. I have a doctors appointment tomorrow and really want to be able to stay home at 38 weeks (next week) and start preparing for my baby and this dilvery. I haven't taken any vacation while pregnant because I was banking on these two free weeks of vacation. I have massive anxiety issues and sleep is nonexistent for the last few weeks... maybe a few hours here or there. What should I tell the doctor to help persuade her in my favor in writing the doctor note to give to work?. I'm in military if you haven't got the impression yet- a little more strict than normal jobs. I know this might sound pathetic but I am soooooo exhausted from work- I don't just sit around- I am actively involved and work full time. I just really need this break.