Thanks for providing more information.
As per your description,you are going in right path for further diagnosis.
GERD can be a possible cause in your case for chronic cough.
And further upper GI scopy should be done in your case.
Other possible potential differential diagnosis may include Sinusitis(as you have cough,stuffy nose,sore throat,post nasal drip).
Laryngopharyngeal reflux disease.
So you can try steam inhalation and saline gargles.
Also add Zantac 150 mg twice a day alonwith Nexium.
Avoid eating meals just before your bedtime.
Take OTC Claritin.
And make an appointment with a gastroenterologist again.
Hope this helps.
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