What Causes Severe Pain In Upper Arm And Numbness In Little Finger?

I have had severe left sided shoulder and upper arm pain numbness in pinky finger and elbows and severe pain when I sleep on left side at night and it seems to be getting worse and feels as if something is slipping or moving when I turn over in the bed I have to hold my arm in place to turn to keep from having so much pain and in this has gone on for several monthsbending my elbows seems to make the numbness or and sometimes a certain way I put pressure or move on my left arm makes the pain worse it s hard for me to pull up your pants or take my jacket off or reach over to shut the car door or check the mail box with my arms