What can I do about chronic post nasal drip I've had for the past year?

I had a septoplasty about 4 years ago. For roughly the past year, I have experienced chronic post nasal drip.I have tried every medication (prescription nasal sprays including Ipratropium, Azelastine, Flonase) as well as singulair and several antihistamines. I have tried nasal irrigation with ZERO improvement. What can I do? I am going crazy. Constantly sniffling, and it just doesn't stop. The worst part is, I can't seem to either completely blow it out, or suck it in.