I got a little worried when I read your post. I have narcolepsy and used to do just what you did. I binged on coffe and caffein for years. As Sjogren's is an autoimmune disorder - adrenal burn out - which huge amounts of caffein causes, is of concern.
I am sure you must have thought of getting tested for narcolepsy? I am not for drugs - but sometimes one type of drug might be less damaging than others - and some of the narcolepsy drugs are not stimulants. How is your nightsleep? and what do you do for a living.
Is wheat all you have cut out and what other things have you tried. Did your doctor test your vitamin D levels, Hb1Ac, Iodine and RBC magnesium? Have him do an adrenal test just so you don't make yourself worse in the long run. I did a number on myself and have worked years to try to repair the damage- not easy...
I was diagnosed with Sjogren Syndrome as well and battled fatigue too. I later found out that I am also intolerant to other foods and after eliminating them I am much better. I don't even need coffee anymore. I do still drink Green Tea because it's been proven to help protect the salivary glands of Sjogren Symdrome patients.