Hi Suz,
I'm sorry to hear that you suffer from RSD also!!

I'm glad you have found this forum - you will meet many great people who i'm sure will try and help you in anyway they possibly can!!
I have RSD in my left leg and both arms. I developed it when I was 12 years old after an ankle sprain and it since spread to both arms after further injuries. Like you, I am always extremely scared about the possibility of it spreading and tend to be very careful.
American RSD Hope (a popular organisation dedicated to researching RSD and finding a cure) conducted a national survey not so long ago about spreading and the results have just come in.
The results said that in 75-80% of cases, RSD will spread but only 8% of all cases become systemic (full body) thankfully.
Here is a link to the article should you wish to check it out:
http://www.rsdhope.org/survey/results.asp
I know it is really hard but please try not and not panic too much. Getting stressed too much about your condition and the possibility of it spreading will only make you worse and more prone to having a spread etc (it's been proven that stress can make RSD worse and/or spread).
If you ever want to talk, please know that I am here for you because I DO understand what you are going through and how hard it is dealing with all of this!!
Take care of yourself!
Alison.