The lights in grocery stores top the list of nerve-janglers. I wear dark glasses to go to the grocery store. Years ago when I was sicker, I wore both dark glasses and a hat with a large brim. if the lights are flourescent, they are of course worse than incandescent.
I had the problems you describe, Dejibo and all, long before MS diagnosis. I can get by better now in a store. Taking that deep breath like Barb 02 suggested makes it better; it's called regaining focus. The music they play gives you the willies. I love it that my coop (natural foods coop) does not play ANY music.
This is an important thread in showing the hidden disabilities we have.
It's common to people with porphyria (which I also have). One of the things which makes porphs lose focus is environmental toxins, one of the worst being either a new rug or a rug cleaned with toxic chemicals. I had to quit my teaching career because of a new rug, and I am not exaggerating. Yes, other things had made teaching more and more difficult, including the lights, but the rug was "the end."