My heart aches for you - as moms we have to champion for our kids and your son is so lucky to have you on his side. It is unusual for a young child to be dx with MS, but it has been found in children as toddlers, so it does happen, so don't let anyone tell you differently.
Be sure to call the MS doctor office and have them put you on their cancellation list, if you haven't done so already. And ask them if it is ok if you call them once a week to check if anything earlier has opened up. Be nice about it, but stress that this is a child who's condition continues to deteriorate.
We aren't always developing new lesions when we have MS - it is only during the active phase - hence the relapsing/remitting part of this MiSerable disease.
We have a ton of information in our health pages, written by members of our community. You can access them through the yellow icon on the upper right side of this page. While you are waiting and understandably worrying, take this time to learn as much as you can .......... the index is accessible thorugh this link-
http://www.medhelp.org/health_pages/Multiple-Sclerosis/MS-Information-and-Resources-Index/show/22?cid=36
This is a great place to learn more and ask questions - I hope you will stick around and let us help you through this journey.
my best to you and your son,
Lulu