My first initial thought when you mentioned headache is that you might want to look into the possibility of a mold infection, rather than a mite problem. This might correspond with the thickening of the wall that was found and there is not answer. Molds can be in the head too and it is most likely the first place it travels because of the sinus cavity. The dirt and chicken coops are notorious for mold.
This is a good post that you might want to take to your practitioner that you're working with.