welcome in H.C.M.
I have gone through your query regarding nasal discharge, post nasal drip
, severe headache
after flu and you had no improvement by antibiotic while injection of cortisone
had proven much benificial.
your clinical history clearly indicates that you are having sinusitis
which is giving you headache, post nasal drip and green phlegm.You felt better by inj of cortisone because it reduces the mucosal swelling thus sinuses gets way to drain out and pain disappeared but soon after these symptoms will reappear.
For confirmation of diagnosis and treatment you should do-
1- C.T.Scan of paranasal sinuses
2- Culture and sensitivity of nasal discharge.
3- Blood- CBC, ESR, blood sugar (F & PP).
By these investigations and a thorough examination one may made correct diagnosis and may be manage accordingly.