Usually neuros will start with the brain MRI because lesions most often show up there first. A spinal MRI may be ordered later if nothing shows up on the brain MRI, or through other testing.
As Rhonda said, though, there are lots of disorders -- some of the neurological, some metabolic -- that "look like" MS on the outside. So the doctor will want to rule out things like thyroid problems, diabetes, other autoimmune disorders, infections, all sorts of other things, before deciding that you might have MS. You may be sent off to have a spinal tap (or lumbar puncture), for example, or have a bunch of blood drawn to look for some of these other things, or have evoked potential testing done, where your brain waves are measured.
I'm sorry you're having problems, and know the waiting is a challenge. Don't be afraid to ask questions; we'll try to help.
...I am not a doctor, nor health professional, and don't pretend to be one, here.....