Suggest Medication For Severe Bronchitis

Hello, ive been diagnosed with severe bronchitis 20 days back. At first, i was suffering with severe productive cough with light green colored mucus, low grade fever at night and chest discomfort / shortness in breath. After physical examination, my GP prescribe me with an antibiotic course for 5 days. The first course of antibiotic didnt help. Then my GP changed the antibiotic and this time he gave me a 10 days course of Klaricid 500 mg and tylenol. After a week or so i started feeling well, the cough went away as well as my low grade fever, but i still had a little chest discomfort. After the completion of my second spell of antibiotic, i went for re-examination and after physical examination, my doc said i still have air blockage in my left lung and he suggested a chest xray. This time i took my Xray to a pulmonologist and hr said that i have severe bronchitis / bronchital changes. He prescribed me with another course of 7 days antibiotic along with a short therapy of Betnesol 0.5 mg, 2 tablets, twice a day for 7 days.

Please suggest what seems to be wrong with me, why the bronchitis not going away as i have already tried 2 different antibiotics spells, and why i am prescribed with a steroid therapy which seems to be a heavy dose.

Btw im smoking since 15 years or so, im 33.

Zeeshan