I'm just sayin', based on my own experience and what I learned from my allergist in an exhaustive (and exhausting!) initiation when I was first diagnosed.

Fatigue is probably the #1 symptom of allergies in general and food allergies in particular.

Leave open the possibility that it isn't necessarily (or exclusively) the synthetic ingredients that are causing your symptoms, but "natural" ingredients in both processed and unprocessed foods. It's very, very difficult to find a processed food that doesn't contain both wheat and corn products. Also soy - I knew there was at least one very common allergen I was leaving out. Reading the ingredient list doesn't always tell you, unless you know what you're looking for.

I'm not saying it's a bad idea to have your thyroid checked, but if your thyroid panel was normal in the fall and you were symptomatic then, then something else is likely to be the culprit.