Terrible in exams...what can I do? Watch
I'm just not sure what I can do about it.
My advise would be to simulate "exam conditions" as much as possible, ie print out past papers/test and attempt in the time limit w/ any distractions and only task being finishing the paper. Maybe tell your teachers about this.
explaining it to your parents/brother/sister/grandparents (only if you feel confident with it)
Hopefully this helps