Ouch!
That truly is a nasty condition to have.

Can you move your arm away from your side, or is it "frozen"? This much I know. If you can move it, do...even if it is painful to do so; because if you don't it can freeze up over night and that is much worse.

What did the ER doc recommend?
Can you get in for some physio? Ultra-sound therapy will often decrease the inflammation and the pain. Massage therapy will often get the mobility back and reduce the pain too. Massage to the neck and back will also prevent compensatory spasms and pain in those areas.

Hang in there Erin. It does get better with or without treatment; although it can take a while.

With love, Erika