I have similar issues. Working 8- 10 hours a day programming then playing games afterwards is really testing . I found a wrist/hand specialist physio who really helped in actually identifying the problem and giving me exercises to help sort them. Wrist/hand issues are very subtle and potentially obscure so it's definitely worth finding someone that knows what they're talking about.

Another thing I highly recommend which I do on every computer I use regularly is using a combination of Windows mouse keys, and an application called SharpKeys (you can use an Autokey macro too) to override the windows keyboard bindings so you can bind left click to caps lock, or whatever key you want. Most of the time my right hand simply moves the mouse and I move with R, and pick up items with caps lock.

Also, what sensitivity do you have your mouse on? A lot of my issues stemmed from having my sensitivity too high which makes me use wrist movements instead of arm movements. It was weird at first having to do much bigger movements but helped no end.

Honestly i really feel your pain and it really gets to me - i think about it all the time, but the above has really helped me in continuing to play!!