My goodness, you have been through the ringer with those doctors.
To get right to the point, YES, blood tests can fluctuate with lupus and can change to negative after you've been on treatment for awhile. From what I've read, a positive ds-dna is very indicative of lupus, especially with all your symptoms.
Can you get copies of the labs where your tests were positive and bring them with you or have them sent to your new doc? And also the notes and records of that first doctor that did those tests and diagnosed lupus. This may help a lot in convincing a new doctor.
Now about
the new doctor...personally, I would find
another new rheumatologist and would be very leery of anyone who refers you to a nutritionist to
cure lupus. I don't think I can link directly to the page, but if you need resources to find a rheumatologist, you might try
lupus.org then click on Resources --> Find Local Resources --> Find a Doctor.
Don't give up until you find the right doctor. The good ones are out there, but for some reason it seems typical for us to go through several rheumatologist (or more) before finding a good one.
P.S. I'm so very sorry about
your sister. The positive family history is important, and I think you're right about
lupus being more common in blacks...at least it seems like I've read that before. But I DO know for sure that being black is NOT a reason to think you can't or don't have lupus!