What Does Dizziness Along With Throat Discomfort Indicate?

For over 15 years or so I have had throat tightness and light headedness and coughing which may or may not be related. The symptoms worsen with time. The throat tightness / lightheadedness was first noticed during exercise, walking up a hill. It now happens every day with mild walking around, walking upstairs, after eating, or with little sleep. The coughing is sometimes mild and sometimes extreme and seems to be worse with cold weather. Sometimes I have to cough when I m in the middle of talking. Breathing in deeply makes me feel like coughing or just out of the blue doing nothing and I will have to cough. Lying down makes me cough. I have tried acid reflux meds for months at a time, and was on anti-depressants for years; neither of which seemed to make a difference. I have 2 cardiologists, neither of which can find a cause for these symptoms although I do have hypertension. I have had allergy and asthma testing and some years ago had an endoscopy, none of which produced a finding. Is it possible these symptoms are diet related? Any other possibilities?