Back pain legs going numb?

Stenosis: Stenosis or narrowing of the spinal canal can cause pressure upon the leg spinal nerves. This would cause both back pain and numbness in legs. This is however not a disease of a 20 year old, so other things need to be considered. See your md for this if not getting better.

See your doctor: For an evaluation and examination. If symptoms persist, you will benefit from nsaids (if no contraindication), physical therapy. Lumbar spine MRI may be needed to better assess if there is a spinal cause to your symptoms. If so, with persisting symptoms, epidural injections may be very helpful. Surgery only after these treatments fail to relieve symptoms (if MRI shows a compressive pathology).