I Am Suffering From Seasonal Allergies From First Week Of

I am suffering from seasonal allergies from first week of May. After visiting the local ENT doctor, I have already completed the anti-allergy and anti-biotic course of 14 days and 7 days, respectively. Now I am feeling much better than 3 weeks ago, but my body is still making excess mucus and I can't stop coughing. I have been suffering from this cough for over a month and now whenever I cough there is a very strong pain in my chest and back bone. I have taken meds, over-the-counter cough syrups, steam, hot beverages, honey etc. I am really tired of this cough now and feeling really annoyed and depressed. I searched my symptoms online and found that more than 80% of my symptoms are similar to the symptoms of Lung Cancer. I desperately need your help, please guide me.