Hi.. Can understand your concern.. As per your complain the scratchy sensation during the day and thick mucus during night and dryness in mouth are all symptoms of DRY MOUTH and dryness in mouth can lead to dryness in throat due to lack of saliva.. Scratchy sensation during day may be due to infection in the throat either bacterial or viral or irritation to throat mucosa due to chronic dryness.. Dry mouth can occur due to a number of reasons and mouth breathing is one of those as the mouth remain open and the air passage through the mouth an throat leads to its dryness and irritation can occur due to it and there are higher chances of landing up with infections in mouth,throat as well as respiratory tract.. You need to work on stopping mouth breathing to prevent dry mouth and throat and it can be done by Tapping the lips at night.. You need to put some vaseline on the lips and put a micropore tape over the closed lips vertically on the centre.. This will prevent you from sleeping with opened mouth and breathing through mouth.. Initially it can be a bit irritating but slowly you ill get habitual and mouth breathing will eventually stop.. In case if you have nasal blockage problem you can use nasal sprays to clear up the nasal passages to breathe through nose.. In case if you still find your mouth dry during day time also you need to look for other factors responsible for dry mouth.. Hope this information helps.. If you find the answer helpful kindly write a positive review and click on found this answer helpful as a token of appreciation.. Thanks and regards.. Dr. Honey Nandwani Arora..