A negative ANA, especially when you've had positive ANAs in the past, really doesn't mean a whole heck of a lot. ANA is a very crude measurement, and as such, cannot even be used to monitor disease activity (any of the ANA related diseases, not just lupus). With your elevated SED rate and ESR, though, something for sure is going on. It sounds like your rheumy has a handle on it. It's been my experience that AI disease can be very ambiguous for the first several years that it starts, and it is very difficult to put a specific diagnostic label on it. My rheumy reminded me at one point that I should spend less time worrying about a diagnosis, and concentrate more on feeling better. In other words--go with how you feel because that is probably a better indicator of what's going on than any stupid lab value.
I hope you feel better soon. Has your rheumy put you on plaquenil yet?
Current dx: Rheumatoid Arthritis
Suspected dx: UCTD/Early Lupus
Current Meds: Enbrel, Plaquenil, Aciphex, Ultracet, Zyrtec, Allavert-D, Zantac, Tylenol PM
Past Meds: Relafen, Vioxx, Mobic, Voltaren, Sulfasalazine, Entocort, Prednisone, Humira, Reglan