If the test that came back negative was your SED rate, that result isn't worth a hill of beans. I'm not sure why some people have an elevated level and others who are obviously dealing with arthritis issues have a normal or close to normal rate. I don't know if it's a swelling issue, type of arthritis issue, or what. It's very odd.
I don't have the other issues you are dealing with, so I can't really say much about them. I know I have/had issues with severe dryness from medications, I know my SED rate is often fine when I'm doing terrible, I have met people who have had debilitating and all sorts of odd issues come about that can't be diagnosed until they find out something they are taking (med or herbal) was doing it to them all along.
I feel for you, it is frustrating not to know and having to deal with all these doctors to help you pinpoint and find the problem. Then you have to hope that your doctors are good ones who care enough to help find the problem and not dismiss you when the easy fix isn't the answer. There are so many kinds of auto-immune diseases out there, even just in the arthritis family alone.....many symptoms cross over each other....it's not always an easy task to figure out.
Hang in there.