I don't have MS (so it appears), but I have quite a few similar symptoms, including dizziness and the related brain fog and fatigue.
Back in 2000, neuro prescribed Provigil, saying "we used to use ritalin
for this" but that Provigil is now favored because of fewer side effects
. Provigil was very helpful for both fatigue and cognition, although I didn't like the late-afternoon "letdown" effect I got with it. It was rather unpleasant.