I have post nasal drip all year round. i use a humidifier, take singulair, xyzal, flonase (2x a day) and it's still there. what's wrong w my sinuses?

Post nasal drip: all year round, all the meds you mentioned and the humidifier may control inflammation / congestion some, but won't treat infection, may be something else in your surroundings is irritating your airways, e.g. a pet, however, you need to see a specialist: an ENT or an allergist / immunonlogist, check aaaai.org or acaai.org for an allergist in your area, best wishes