You need to rule out leaky gut syndrome and histamine intolerance.
So, could you possibly have oral thrush? I'd get that looked at as this is easy to treat. Otherwise, if you have allergies, those often don't just 'go away'. My son is on year round allergy medication. It sure keeps him feeling better. Post nasal drip can cause a sore throat and he also has itching which makes him try to clear to itch it which can be irritating in and of itself. Have you ever seen an allergist? My son's allergies are pretty straight forward. Responds well to otc allergy meds.