I agree with RichT. you need to see a specialist who deal with only spinal issues. Either an orthopedic surgeon or and neurosurgeon who specializes in spines only.
Sounds like you are in dire need of an MRI and possibly other tests to determine what is exactly going on with your spine.
While percocet may be helpful to you for the pain, it is not a way of determining what is wrong with your spine.
Once you have a diagnosis, you can properly be treated for whatever is causing your pain.
And please, as RichT said, DO NOT GO RIDING A MOUNTAIN BIKE OR ANYTHING ELSE UNTIL YOU ARE PROPERLY DIAGNOSED.
EXERCISE CAN BE WONDERFUL TO HELP WITH SPINAL ISSUES, THE KEY IS THE CORRECT EXERCISES AND DOING THEM CORRECTLY.
Until you are properly diagnosed, the wrong exercises can make matters worse.
Good luck
Fran