See a neurology , it may be a nerve pinched on your back...
Do you eat bananas? Some people who are missing potassium start getting numb or cramps. Try a few bananas if they do not help, I would go see a neurologist. This sounds like something might be going on with your nerves. Good Luck!
it is becoz sumtymes whn the blood is nt able to go to fingers,then it causes this numbness,fr ex if u sleep wrong and if u put hand under ur head instead of a pillow,see wht happens whn u wake up next morning