Work. Is. Exhausting.

I'm a teacher and this year got thrown into an AP high school subject I was not expecting to teach and know nothing about. In addition, I am planning for two other brand new subjects by myself. So far, I've worked 90+ hours a week and pulled two all nighters. All within the first 3 weeks. I'm so exhausted, and although I would love to quit, I would lose my teaching certificate, which would be the end of my career. I worry for my health and the health of the baby, not sleeping, resting, and the stress can't be good! Does anybody have tips on how to deal??