Have you spoken to your school/ college/ uni ect about being given possible reasonable measures to help you complete your exams in regards to your condition?
Like if you find it less painful to type asking if you can complete exams on a word processor?
Asking if you can be given extra time so you can complete it without being in so much pain from rushing? Along with to help with the concentration issues and needing more time.
Maybe even asking if you can use an ergonomic chair to prevent excess pain?
They are supposed to put reasonable measures in place for students with disabilities so that they are on a level playing field and can complete their exams/ assignments with their condition affecting them as little as possible.