Hi Dear , Welcome to Health Care Magic Team. Understanding your concern. As per your query bad cough caused by post nasal drip is pointing towards sinusitis .There could be many causes for sinusitis like cold ,nasal polyp,respiratory track infection, septum deviation and weak immune system due various diseases. Treatment of the sinusitis depends upon the cause .If the sinusitis is due to bacterial infection then doctor can prescribe antibiotics along with antihistamines and decongestants which relives the symptoms like post nasal drip. Antihistamines are also effective if the causative factor is allergy. Apart from this you should take steam twice a day which will give relief from congestion , also do warm saline gargles. You should consult doctor so that he can diagnose you properly to find out exact cause , he can review symptoms and take physical examination .Doctor can refer for CT scan and blood test . Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry Maheshwari