Oropharynx problem causing gagging

I have bad allergies and possible LPR. Since I was little I always had this problem in my throat that I just assumed was normal until now.

My problem is something in oropharnyx area (right where your gag reflex is) I would get an involuntary urge to gag or retch. I however have never actually gagged because when ever I get this feeling I immediately have to "force myself to control it" by swallowing hard or holding my breathe and and tensing that area or w/e. I have noticed this happening when I am running and even normal things when I am just talking and today when I was practicing the flute. My dad and I came to a conclusion that it might be my tonsils because my mom has abnormally LARGE tonsils that hangs down her throat and this problem seems to be in that area. My opinion, it has something to do with the way I breathe and with the way the air is going down. This makes me believe that part of my throat isn't properly structured. I have had an endoscopy and my ENT put that fiber optic scope up my nose and looked at the top part of my throat. We originally thought it was my tonsils but he said my tonsils were normal size.

The main thing that is really bad about this, is my inability to run and exercise because of this problem. Normally when you run you eventually get tired and you stop once you reach your limits. When I run, about 30 seconds into running I get that feeling of having to retch and gag. I am barely able to even do 1 mile, that's how bad it is. This is why I really need someone here to shed some light on this and give me some good information so I can take it to the doctor and figure out what to do.

I have told doctors about this and one doc said about the post nasal drip causing it and the other brushed it off and said I had a hyperactive gag reflex and I just have to live with it which is impossible.

What I want to know is
Is it possible that there is a structural abnormality in my throat that can cause it. I really need someone who knows a lot about this. Many people have told me anxiety and some random other things but I've had this ALL MY LIFE and it's never gone away and its not anxiety or anything like that.
If anyone has any other idea what this could be please help me out here.