Work and morning sickness?

I’m a teacher, so fortunately I have had weeks 4-5 off. However, I go back to school soon and I’m worried about the constant nausea, gas, and vomiting. I teach high schoolers; I have to be at my A game every moment of my day. I don’t know how I’m going to make morning sickness (MS) and work coexist.

Should I tell my supervisor about my situation now or should I wait?

Also, does anyone else have success stories about handling MS in high stress jobs?