What's a good way to get rid of post nasal drip?

I have allergies. So I'm taking Zyrtec and Claritin and Flonase spray. Still I'm getting lots of post nasal drip that is causing me to get phlegm in my esophagus and it is making me cough - a deep hacking one. It is not as bad as it was. It has been over a week now. Numerous neighbors are coughing in my building too. The phlegm is clear. A co-worker said hers was allergies to mold - I'm allergic to mold, trees, gr and dust mites and something else outdoors I forgot... Any help is greatly appreciated... I'll go to the doctor's this week if it doesn't go away. I'm on probiotics now... I'm taking generic DayQuil as a cough suppressant