Severe dry mouth and don't exactly know why?

okay so here is my concern, i have had congestion and allergies for several months including fatigued and tiresome. i never really took meds for it either bc i constantly forget.i take amoxicillian when i remember but i have to open capulet bc i have trouble swalling. i also have hypothroidism. here lately i have had dry mouth even the lips and not sure why. i breath alot through the mouth at night being congested and recently noticed myself drooling in the few min. that i am still awake before going to sleep. i just checked my blood glucose(not diab.) in april and score was 90 so don't think that thats something i should worry about. can anyone give me clues to what it could possibly be?