Sounds like you have an mtb with grip shifters...
Best advice would be to quit your job and find something that does not cause these repetitive stress issues that interfere with the joy of cycling.
But seriously, thumb shifters mounted on top of the handlebar can be set up so you can use gross motor movements instead of micro movements to shift... The palm of your hand can push and pull the shifter instead of pushing with your thumb and there is no twisting involved.
For road bars, bar end shifters can be pushed down with the palm and pulled up with almost all your fingers so put very little stress on the thumb and wrist.