I've got similar issues as you in my left had (crushed it while working on my old jeep). Gets tight when weather changes, etc.
These guys have given you some great advice. I would echo:
See a dr - especially if you have good insurance, this is important for your health as he can recommend therapy, etc. to help. This is also important legally, as having documentation is key for any sort of disability benefit.
Invest the time in workspace ergonomics - desk/chair/monitor/keyboard position, pointing device
Go for a lighter switch and try not to bottom out - the modified clears are a good example, but also the 65g Zealios might be a good choice for you.
Investigate voice input - these have come a long way in the last few years; it's still cumbersome to navigate the computer but if you are doing long strings of text (email, papers, etc.) then this can help you a bunch.
+1 to all the points above.
I'd go so far as to recommend going even lighter, with 62g Zealios and some lube for them. They're smoother and this makes them feel even lighter than 62 ErgoClears even before lubing, but they still have the same tactility. You should also investigate the trampoline mod, inserting little pieces of rubber into the switch stems to reduce bottom-out shock. I recommend the silicone balls from IMSTO since they're consistent and easy to install (
http://imsto.cn/index.php?route=product/product&path=61&product_id=88).
In terms of board designs, there are a few options that can reduce the amount of finger movement required, such as the Atreus (
http://atreus.technomancy.us/) and I'd recommend learning your character layout of choice on something like that, assuming you can put together a set of layers that suits you (it's a minimalistic board).
If you learn a layout that's very different from QWERTY on a proper ergonomic board, it won't affect your normal typing skills, so you can still type on a normal board whenever required.
Another advantage of such a small ergo board is that it's portable, so you can carry it with you if you know you'll need to type for while wherever you're going.
I like Cherry profile keycaps (specifically GMK doubleshots or Gateron PBT) on really small boards, but this is just a personal preference.