Hi, I just had similar case. I had been coughing every evening, like choking on my own saliva since June. Then every month I will have sorethroat, mild fever. Completed antibiotics, doesn't help much. This goes on until October when the cough got significantly worse. Went to my GP friend, did Influenza test, and then I found out I'm influenza A positive.

After that influenza, the phlegm become worsen, annoying, lasting for one more month. And then by December... it suddenly gone. I'm back to healthy, no more evening cough.

So in total, it took me 6 months for the condition to resolve by itself, which I think, is not something I would recommend anyone. So maybe try find a respiratory specialist because it is a very annoying 6 months of coughing. GP can't help with this condition.