Question
For 4 years i have had numbness in my neck when i sat on a hard chair, it is relieved when i get up and walk.
I had an xray of neck which was fine, i have put up with it, but now it is there most of time and spreads down my spine and up the back of my head, i am getting severe headaches. What could be the cause of this, it is affecting my every day living, especially when driving, sitting and using computer. i would be grateful for any suggestions.

Answer
Without an examination, it is hard to diagnose, but is sounds as if there is some undue tension, probably originating from the mid back, and pulling up into the neck.  There are muscles that originate there, and travel upward to the neck and the base of the skull, and when tense, can pull and cause neck pain, headaches, etc.  You may want to find a good chiropractor that will address the tension and make sure there are no misalignments causing the problem.