From the description of your symptoms, most likely you are suffering from a slipped disc, the persistent numbing feeling is cause by the nerve "pinch".
We would need to do a thorough check up and a MRI scan to fully investigate the cause of your symptoms and the severity of the condition. Although most slipped disc are not dangerous, some slipped disc can be huge resulting in severe compression of the spinal cord, this can lead to a davastating condition called "cauda equina syndrome" - you will lose control of your legs muscles, your bowel and your bladder (the red flags as mentioned by Dr. Dinesh).
So we recommend that you go and seek treatment with an Orthopaedic Surgeon and we will able to advise you further.
Hope it clear some doubts for you.
Cheers,
Dr. Henry Chan
