I've haf this lower right hand pain which has come and gone over a few days. i have an old ergo keyboard. should i switch?

Yes: Yes, but if the pain does not disappear, the cause needs to be identified. It can be tendon/joint problems (arthritis, tendinitis, etc.) or nerve disease (carpal tunnel syndrome, etc.). Many of these conditions are treatable and the tests (blood work, x-rays, nerve conduction tests) are available through your regular physician. If no abnormality is found, the problem may still be ergonomic.

Maybe: If keyboard is lower than desk surface, tilt the back edge of the keyboard slightly down. Keep wrists in a neutral (straight) position—not bent up or down. Keep elbows at a slightly open angle-90˚ or greater. Keep shoulders relaxed, and elbows at side. Don't use wrist rests or armrests while typing-only while resting. If you have a broad chest, consider a "split" keyboard.