Welcome in H.C.M.
I have gone through your query regarding continuous cough, feeling of obstruction in throat, post nasaldrip and all these for last 4 monthes. you have taken medicines for this but no relief till now.
Considering all aspects of your clinical history it is evident that you are still having sinusitis
and this sinusitis is continuously giving out infected discharge from sinuses , which you feel as post nasal drip
. Till this drip is there your throat infection
can't be cured.
To manage it you should do these basic investigations-
1- C.T. Scan of paranasal sinuses
2- Culture and sensitivity of throat swab.
3- Gram's staining of throat swab.
4- X-Ray of Chest.
With the help of above investigations and their co-relation with clinical examination by your ENT doctor diagnosis
will be finalised and ultimately curative treatment may be planed.