I cannot figure what is wrong ?? Sinus or Throat?

[Leaf2]

About a 6 weeks ago I experienced a cold.  From the time of that cold until now, I have experienced a chronic cough.  The cough produces small amounts of thick yellow mucus or phlegm.  The phlegm does not begin until about 45 minutes after I wake up in the morning and lasts, usually, for about 3 hours.  

At night, my throat tends to be dry and itchy.  I also have experienced some sinus congestion in the morning.  I have not experienced any other symptoms (e.g., fatigue, fever, chills, etc.).  Not even a sore throat.  And I do not smoke.      

A physician prescribed flonase, amoxicillin, and promethazine.  I have been taking all three for the past 4 days with little or no improvement.

I cannot figure out if the source of my problem is my sinuses or my throat, or something else.

Any help would be appreciated.

[National Jewish]

In a person who has a normal chest x-ray and who doesn

[Ellis7]

It might be postnasal drip from nasal region getting into throat.
Flonase should take care of that and nasal congestion. Be sure to use it according to the prescribing instructions [pdf] at
www.flonase.com
shake gently before using
initial pump priming is 6

It can also be more effective after doing a warm saline nasal wash. See;

http://nationaljewish.org/medfacts/nasal.html
Nasal Wash Treatment
Excerpt
"Method 3 - Use your hands for this technique. Pour some saltwater into your palm, then sniff the liquid up your nose, one nostril at a time. Blow your nose lightly. This technique may not be as effective but may be used in some situations. "

[Clotter1]

Wait a few more days and if your condition doesnt improve go back to the doc, anti-biotics take a few days to start working.