MY ARM IS GOING NUMB FOR LONG PERIODS OF TIME.

MY ARM IS GOING NUMB FOR LONG PERIODS OF TIME. IT STARTS IN MY UPPER ARM (BICEP/SHOULDER) AND GOES DOWN TO MY FINGERS (MAINLY THUMB AND POINTER FINGER BUT OCCASIONALLY ALL MY FINGERS WILL GO NUMB) SOMETIMES IS SO BAD MY WHOLE ARM JUST GOES LIMP AND I DROP WHATEVER IS IN MY HANDS ( PENS, CUPS, FORKS ECT). WHAT SHOULD I DO? ITS BEEN ABOUT A MONTH NOW .