What Causes Numbness In Left Arm Radiating To Underarm?

MY LEFT ARM GOES NUMB STARTING FROM THE ARM PIT DOWNWARD. OCCATIONALLY, IT FEELS LIKE THE LYMPH NODE GROWS TO THE SIZE OF A BASEBALL AND TURNS INTO A BOA CONSTRICTOR AND TWISTS EVERYTHING INSIDE MY ARM. WHAT MIGHT BE CAUSING THIS?
PLEASE REPLY TO YYYY@YYYY
THANK YOU SO MUCH FOR YOUR TIME.