I Have Had A Chronic Cough For Many Years Without

I have had a chronic cough for many years without any cure......I have taken allergy injections for years, asthma medication and nothing helps. I recently used chlorphenira tablets and that helped for about a month, but now I'm back to coughing........I think I do have PND; I use nasal rinses but nothing seems to stop this explosive cough that comes out of nowhere.