Hello Alison
Here are a few sites for you. I hope they help!
http://www.angelfire.com/wi/rsdhopeteens/personal.html
http://www.rsdescape.com/RSD%20In%20Children.htm
http://www.rsdescape.com/
http://health.groups.yahoo.com/group/rsdhopeteens/ (search on yahoogroups.com for more yahoo RSD teen groups)
http://fightingagainstrsd.tripod.com/
These aren't forums, they are just sites for children/ teens with RSD. You can find the email groups at yahoogroups.com though.
I am 17, have full body RSD and I know what you're going through ((hugs))

(who Ada mentioned above

)
It is really hard going through this when you're young... it stinks! But hang in there. You already have my email address if you need me (hugs).