Hello Welcome in H.C.M. I have gone through your query regarding thick saliva in mouth with dry lips . After analyzing your symptoms and co-relating them it appears that you have anxiety too much, because anxiety is one physiological factor producing dryness in mouth beside this anxiety is always associated with hyper acidity which again is creating dryness in mouth. As you have told that you are having post nasal drip this signify that there is sinusitis as well and because of it there are chances of nasal obstruction so oral breathing becomes alternative and whenever anybody breath through mouth, the air flow always causes dryness in lips and mouth cavity resulting in thick and sticky saliva. Therefore it appears that all above factors are present in your case and developing thick saliva, dryness of mouth and lips. Regards.