This is currently a little up in the air due to a recurrent problem I have with the thumb on my drawing hand, I've had this on and off for a few years now but just recently I have felt it troubling me and in this last week it's really become painful so I've stopped for a while.
The doctor said it was a form of arthritis... but I may go back to see if that's still the case. The joint is quite swollen and hurts when I press down, and as I press down quite hard while inking this is where the issue lies.
An option is to go all digital and ink on the computer, I'm not sure how I feel about this as I spend all my working day glued to a Mac and I don't much fancy the idea of doing it at home as well. Add to the fact that I like working on paper this is probably a no-no.
I'm hoping it will go better on it's own, or with a visit to the doctor and maybe some physio... time will tell, I just hope this won't mean the end.