Hi Joanne,
I am sorry you had to come join us. We all know how terribly scary it is in the beginning and how powerless it feels. But there is hope. Cleveland Clinic's CRPS bigwig Dr. Michael Stanton-Hicks says 80% of people improve over time.
Supplements, antioxidants, and stress reduction all help. Try to control anxiety. You want your nervous system calm all the way around. Keep pain under control instead of trying to push too hard through it. You don't want to get entrenched in those pain pathways.
Until you get out of your cast (which will help a LOT) wiggle your toes, do bicycles, anything you can to keep blood moving. Avoid alcohol and caffeine. Elevate as needed. Once out of there, start PT and get in a pool if you can for graduated increase in activity. Gentle exercise that doesn't cause flaring is key.
You may benefit from a short round of oral steroids. They are considered a frontline treatment in early disease at a dose of 10mg three times a day for 10 to 21 days. (taper if needed) If you have no contraindications to them ask your doctor. They are listed under the Dutch protocols and also Dr. Stanton-Hick's protocol if you need a reference. Some people do well on an alpha-blocker like clonidine. There are treatment options even when you can't exercise the limb.
There is a lot of great info here from a non-doomsday, caring and respected CRPS doctor. Dr. Pradeep Chopra "CRPS Diagnosis and Management"
http://www.youtube.com/watch?v=s3LKhOZ8mAM
I am glad you were diagnosed so early. That is great for your prognosis. Remember that progress can be slow with this but gains will come. If you are not making progress once you're out of your cast and start PT, consider follow-up imaging to make sure everything healed up okay. Let us know how you are doing and get better soon!
Sending hugs and healing love,