I injured my back while in the Army, and of course i didnt mention anything so it kept getting worse. Seen numerous specialists, had MRIS, XRays, Blood Tests etc. and nothing has come up. I've had pain for 2 years now and theres been no improvement.
Back marches were the killer. I passed out while doing a 10km because the pain became too unbearable, and thats when they found out i had a problem.
It will come and go, but anything can really bring it on. Sitting or standing for long periods of time etc. for example. And at the worst stages i can barely move and cant do anything but lay down.
I could just drug myself up with pain killers, but you gotta be fully focused in the Army, and wouldnt want to jeopardise anything important. This is why i had to get out.