Sinus Drainage, Cough, Phlegm, Feverish Taste, Bad Breath, Coated Tongue
Your question is a very good one and I will work on providing you with good information and recommendations regarding what is going on.
As far as the change in your breath as well as the changes related to your tongue I really think this is most likely related to mild to moderate degree of esophageal reflux.
Esophageal reflux is a very common cause of persistent or intermittent cough. You may not have significant symptoms of the burning sensation in your stomach or of the typical acid reflux symptoms which many people associate with a harsh acidic burping sensation.
I often refer to this as a subclinical acid reflux. However, this could be what is contributing to the changes what you are experiencing related to the cough as well as the changes related to your tongue.
In order to test this hypothesis I recommend that for the next four or five weeks on a daily basis that you take one tablet of omeprazole. This is the same medication which is available in the namebrand Prilosec. This is typically a 20 mg tablet that you would take just prior to eating breakfast. Again I recommend you do this for the next four or five weeks on a daily basis. At that time point you can reassess to see if your symptoms are moderately or significantly improved. I am confident that you will feel better by that time.
I thank you again for submitting your question. If you have any additional questions I would be happy to address them. I look forward to helping optimize your state of health.
Sincerely,
Dr. Robert.