I have had the same issues with migraines, dizziness, etc.. The only thing that took it away was antibiotics. In terms of the flu and fatigue feeling, eliminating gluten, starch and sugars helps a ton.
I am on long-term antibiotics now and it is helping my head and sinus issues. I also eat organic yogurt everyday and take probiotics.
The diet didn't take away my AS pain but helped my fibromyalgia a lot. I am still trying to figure out what to eat and what not to eat.
Hope you can get on a better track soon.
Meds: injectable MTX, Simponi, daily hydrocortisone, pain meds, NSAIDs, Methylprednisone for flare ups, Armour thyroid