You need to get a CT scan of your Paranasal Sinuses. This will highlight the hidden infection in your sinuses that is causing this problem.
Next Steps
Use this app to find a good ENT Specialist experienced in treating Sinus Infections. Let patient feedbacks guide you to select the right doctor & discuss my suggestion with your doctor. I am sure this will lead to a resolution of your issue. If you are able to come down to Bengaluru, do drop into my clinic Healthcare@Basaveshwaranagar and I will personally help you out.