Reflux is like regurgitation Of stomach juices in the esophagus.  It generally occurs when the valve between the stomach and esophagus is Lax and allows the return of stomach fluid in reverse direction which otherwise should not occur.  Heart burn is the common symptom of reflux ( GERD) though occasionally patient may not have symptoms in spite of having the reflux.  Endoscopy,  pH studies and esophageal manometry helps in diagnosis,  though every patient need not get all these investigations done.  In your case,  as you had diarrhea,  which is not a symptom of reflux.  ( needs proper clinical evaluation)