What Causes Persistent Cough With Green Mucus?

Dear Doctor,I stay in UAE dubai, I ve been having monthly persistent cough for 3 years now.Every year with the weather change to summer during the month of April I fall sick with fever cold n flu, which recovers in 2-3weeks, but the cough remains for 2-3 months and gets worst overtime.Past test have shown +ve microplasma results..I ve taken seretide diskus(didn t work this year) changed to Flutiform (didn t work) This year s test: - chest xray is perfectly fine - liver blood test shows, high bilirubin = 40 mol and Direct bilirubin = 12.06 Mol (recently done) - basic allergy test (doesn t cover seasonal allergy matters) was all negative. (recently done) Most recent prescribed medicines by ENT doctor: - Gupisone (3 tabs daily for 10 days) - take prob and Klacid (for acidity preventiom) for the above I m currently on my 3rd /10 days. Doctor has not been able to find the cause to my cough. Cough is still there since beginning May, 16..sometime with green mucus and sometimes on white thick spit.. Please help me understand as per your expertise what could be the case and any suggested solution. Thank you very much