What Causes Numbness On Left Arm,leg And Shoulder Blades?

Hi,I have been experiencing numbness throughout my entire body but especially my left arm, right leg and muscle area between my shoulder blades since Monday. I have also been extremely tired. I am beginning to feel somewhat better but still have a numb feeling in my left arm and right leg. This has happened to me at least two other times within the last two years. What could it be?