Shoulder Sling discomfort?

I recently hurt my shoulder at work. The ER gave me a sling, some pain killers (which are making me sick to my stomach) and naproxin. Since leaving the ER every time I try to remove my sling radiating pain starts in my shoulder and goes all the way down to my finger tips. My neck/upper back is killing me from supporting my arm. I don't know what to do. I have a follow up appointment on Monday but I'm not sure if there is a way to help ease the pain. Any comments/suggestions are welcome!