I had the same thing happen with my left hand and had to train myself to write right handed. It was a drag, but it worked. Finally I got tired of the RSD ravaging my arms, hands, legs, feet and went to a doctor who started ECT, electro convulsive therapy. I've had treatments for a year now and am able to lift weights, ride my bike, work in the yard, and actually have gone back to work part time. If you want to know more about this, let me know.
Best wishes for you as you experience this mysterious disease.
Friends,
Sylvia