I'm going through the same thing. I not only have pain in my hand/wrist, but pain in my shoulder and upper/mid back (right side). I've already been through physical therapy. What I do now is to try and not use the mouse as much as I can for other tasks (keyboard shortcuts). I also use my mouse on the left side when I'm at work. Also, try to get a mouse that is ergonomic for the right hand (that is, it tilts to the right so that your right forearm does not have to rotate to the left as much). Try the Logitech MX500, or the Intellimouse explorer.