Are you doing all the insomniac treatment recommendations? No caffeine in the afternoon, no electronics for a few hours before bed, warm baths/exercise in the evening but at least an hour before bed, etc but there’ll be a list on the NHS or somewhere.
If you are I’d suggest telling your parents that you aren’t sleeping/the meds aren’t working. It’s horrible to be tired, I can’t imagine what three days worth of tired is like. I hope you can get this sorted in time for exams, otherwise you might want to get a diagnosis for extenuating circumstances!