Yes, it really sounds like you just need a new more understanding rheumy to get you on a better track to feeling better! Perhaps a different cocktail of meds so that you are not in so much pain and can function better at work. As far as your job goes, non-profits such as the Goodwill etc are normally pretty understanding, maybe they would be willing to give you a different job within the store, one that is not so physically taxing, or part-time. I was going to suggest a letter from your rheumy, but this may need to wait until you find a better one! Honestly there are days I think I could use disability myself! but I am only 40 and still have many productive years ahead of me and prefer to keep working and thankfully my rheumy is understanding and my employer as well of what my limitations are so far! Many here have had to hunt for a better rheumy...I don't know why some are the way they are
Obviously they don't have joint pain!!
Hang in there!