Sorry to hear that, Moya. I've always wondered whether I would suffer any ill effects from calligraphy like this, and really appreciate the tips others have shared with you. I hope they help! For my part, I also wanted to share a recent issue that's come up.
Five years ago, when working in a job that required some repetitive lifting above my head, I suffered severe shoulder bursitis (required a cortisone injection) in both shoulders. I haven't really had any problems with it since, until I recently finished a batch of calligraphed envelopes. There are a couple of factors at play, but this is one recent variable that seems to have been the trigger. It makes me a bit sad that calligraphy could be the cause of my shoulder pain, but fortunately I've found some shoulder strengthening exercises (and applying ice) that are designed to prevent this problem. Sounds like from Estefa and WJTury's comments that this strengthening and warm ups are important for hands and fingers, too. Think I'll try (but I'm pretty bad at sticking to these kinds of things) add that to my list of strengthening exercises.