1. Seek medical attention. Pain is a signal of something wrong. Get it fixed. I had severe pain in my right shoulder that turned me in to a left-handed shooter. It turned out to be compression of my cervical vertebrae. It took six weeks of physical therapy to fix the problem. Now I only have occasional pain in my right shoulder that is a signal that I need to keep up with my exercises. The cause of the problem was that I have been rear-ended in my car seven times! Can’t undo the car accidents, but the physical exercises and stretching of my neck and shoulders have allowed me to regain 90% of the lost range of motion I had and has eliminated 90% of the pain.
2. Find and ELIMINATE the cause of your RSI. Otherwise it will only get worse until you will not have the use of your elbows.
3. Once the proceeding steps are done, work on your shooting technique as often as possible!