To prevent this kind of thing in the first place: Stop typing at regular intervals, stand up, and run your fingers and wrists through a range of flexion and extension motions while moving your arms around, especially over your head and back down again. This will get more blood flowing in the area, which helps. Strength training of your wrists, shoulders, abs and back helps. Wear wrist braces at night. People often push their wrists into strange positions while asleep - this will prevent that. But do not wear them any other time - they will cause muscle atrophy which makes things worse.

You've waited a while though, so you'll probably need to stop typing entirely for a month to let the inflammation go away first.

JWZ is worth reading on this. http://www.jwz.org/gruntle/wrists.html

My final advice: try occupational therapists and physical therapists. Physicians aren't as good about knowing specifically what to change about your behavior and how to get you to do it. The better occupational and physical therapists think about these issues constantly.