I developed RSD after an injury to my ankle when I was 12 years old. I fell down some stairs and sprained my ankle and my RSD started after that. It took 4 and a half months for me to get diagnosed and it has since spread to both my arms after further injuries (both falls).
I've heard that 90% (if not more) of RSD sufferers develop RSD after either an injury or surgery. It is very uncommon for RSD to start spontaniously, though isn't impossible.
I'm sorry to hear that you have RSD!

You will find many great and caring people here who i'm sure will try and help you if they can so please don't be afraid to ask any questions you have!!
Take care and a big, Welcome to Neurotalk!
Alison