Confused. Wikipedia says symptoms of post nasal drip includes wheezing n difficulty breathing but why doc here says post nasal drip does not cause it?

Post nasal drip. Does not usually cause wheezing or difficulty breathing. Sometimes whatever is causing the post nasal drip (a cold or allergies) can also trigger asthma or reactive airways which is really the cause of the wheezing/difficulty breathing, not the post nasal drip itself. Don't believe everything wikipedia says. A lot of it is great information, but not all of it.
Agree w/your doc. With all due to respect to dr. Wikipedia (actually an excellent source usually), i don't think post nasal drip causes bronchospasm, which is what you're describing with wheezing and breathlessness. Those are symptoms of asthma. I would go with your doctor's opinion - in my opinion!