Whilst I am not medically qualified and couldn't diagnose, I have just had a think about what you said and it is a bit familiar to me.
Do you get 'pins and needles' too ? This is something that is caused at times a compressed/pinched nerve. Numbness is a similar problem, a body alarm to let us know that something has gone wrong. This can often just be a spinal joint out of alignment, which can be helped normally through treatment by an osteopath. Osteopathy is used to relieve the compressed/pinched nerve by reducing the muscle tension. It also realignes the spine and can improve joint mobility.
However, in some cases if the problem is left unattended, then degeneration and permanent damage could occur. The result will be a more severe, long term pain and numbness.
Just a thought. As I said before I can't diagnose anything but the above might be of help to you. I do hope so.