I havae had the same problem and I had it when I was in my 20's as well, soit was not arthritus.
In between quilts (if there is such a time) I found excercise works. I go to the gym regularly and they have aNautilus machine that I call the quilter's machine. It is not a comon gym item, but it really works. It excercises the small muscles in yur hand and wrist.
As you may not be able to find one, you might try:
1. a small weight (2# -5#), hold it in your hand and wist your wrist about 12 X both hands. (like turning a door knob)
2. a squeeze weight (pick up at a sporting goods store -- I think they come different strentgths) squeeze 6 X to start, both hands, and work up to 12 X.
You need to strengthen your thumb muscles, ligaments, etc
My discomfort is gone, baby gone.