You want to minimize continuous, repetitive use of the same muscles.
* Whenever your hand feels pain, stop typing, and take a break.
* If you have a PC at home and work, you may want to have one type of mouse at work (standard) and another at home (ball and button). Use the mouse with your right hand for half an hour, then switch to your left, then your right. If your right hand uses a mouse and hurts, use your left hand for the mouse half the time! It takes a little adjusting, but it is better than hurting your hand.
* People tell me this gets progressively worse and worse if not dealt with. You're looking to deal with it which is good, so keep on top of it.