Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern..
As per your complain it seems that you have infection and inflammation in the sinuses causing 
Sinusitis leading to 
post nasal drip.
I would suggest you to consult an Otolaryngologist and get evaluated and a thorough clinical evaluation and investigations like PNS View or MRI of sinuses can help in diagnosis  and treatment can be planned accordingly..
In case if Sinusitis is diagnosed the you can be advised to take a course of antibiotics like 
Augmentin or 
Levofloxacin, anti-inflammatory painkiller like Ibuprofen, antiallergics like Levocetrizine, decongestants like 
Phenylephrine, mucolytics like Ambroxol..You can also do steam inhalations, use decongestant nasal sprays and do saline nasal irrigations..
Do warm compresses around the nose..
Avoid chilled foods and airconditioned atmosphere..
Use a humidifier in your room..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.