I've been being treated for allergies for about 25 years (I am almost 60). Post-nasal drip has always been a part of that to some degree, but it has gotten worse the last few years. I relocated some years back to a more allergy-prone region, so that could be a related reason. (Note: Earlier I suggested AstePro nasal spray, which is over the counter. Another responder told you she uses azelastine spray when things are bad for her. They are the same thing: one is a brand name OTC and the other is a generic Rx.)

I had postnasal drip for years and sometimes sinus pain but no infection. I would go really slow and some of the powerful things people recommend. The doctor told me to use saline rinses like netti pot, to take allergy pills and prednisone spray. After doing this for a few weeks, my eustachian tube valves shut down and over a year later they are still shut down. You are very young to do anything extreme, I suggest getting rid of dust and old paper products, and to avoid smoke if someone in your house smokes. I stopped using so many dairy products which helped. I drink hot tea at times and also coffee with non-dairy creamer. I also got cough drops, and that seems to really help.