I forgot to include these sentences. Thank you.
1)If you don't want to catch your teacher's eye, you'd better not yawn. The doctor prescribed a painkiller to be taken (is "to use" possible?) twice a day on a full stomach.
2)My leg hurts/aches/is sore/ I've got a pain in my leg. I caught measles when I was five years old.
3)If I were you, I'd take a teaspoonful of cough syrup before going to bed.
4)You can nod your head to say " yes " and you can shake it to say "no".
1. "to be taken" is best.
Everything else is fine.