I got my ssdi in two months (unheard of, hey?), my pshyc made sure to note that the chronic pain would not let me sit or stand for more than 15 minutes at a time and that with the pain and fog I could not work more than 3 hours a day. I started on the fmla long term disability through work and my phsyc did all of the paperwork for my ssdi. I hear that I got very lucky, but it is your limitatations that will give the weight needed for ssdi.
hope this helps,
gentle hugs, Cat