Shoulder pain (cannot sleep on left side)

HI
I cannot sleep on my left shoulder for more than half an hour. The pain starts in elbow and remains there for less than an hour. I feel streching in elbow. The pain started after a day when i did "Biceps curls" for three days and i was feeling something in middle of my shoulder. Its been one year, i have been to neurologist as well but no good. MRI is good.
My guess some nerves/vain are pressed while sleeping on shoulder. .
Thanks Tweet