I've been told I have sciatica, but nobody knows what is causing it. It's very erratic in that the pain can start at any time from the simplest movement then be gone just as suddenly. So I can't say physical activity is a definite cause, but it does usually act up after I walk any extended distance. I'm not really sure if a gym class would be good for this, and I'm not really sure what the process is to get excused from the requirements is or even if I could be. What should I do?