Rheumatoid Arthritis Treatment

My Dr informed me 30% of those with RA test a false negative. A more specific test also came back negative. Dr has not ordered any more tests in re Lupus. How likely is it I tested a false positive for Lupus and a false negative for RA?

I am interested in finding out what medications will not exacerbate my ulcers.

I was diagnosed with osteo years ago, but lately I’ve had severe swelling in my ankles and knees, with fluid retention, I thougt that was only with rheumatoid.