I know exactly what you are going through. I have been fighting candidiasis for over a year now and brain fog has continually been my worst symptom. I am taking oral H2O2 (Hydrogen-Peroxid) right now so the brain fog has gotten ten times worse! Hot detox baths are the ONLY thing that lighten it...it has not gone away, but I do have times when it is better than other times...it's an awful, awful feeling. I have also been on a gluten/dairy/sugar/allergen free diet for the last year. It sounds like you may candida as well since you are sensitive to carbs & sugars. If you come up with something that takes the brain fog away, please let me know. I have tried almost everything!!