ahhh ye olde self-diagnosed medical condition
the greatest mental block of them all
guess what tho, my arm and hand hurt when i first got into long streams. They also hurt when i come back after a 3 yr break now and try to do it again because I got soft. They didn't hurt after I trained them the first time and I know they'll stop this time after awhile.
Now, if you actually have RSI it could be a different story, but what you're describing sounds like you're just starting to get into those stamina intensive streams, not that you have RSI. Go see a physician if you really are concerned.