Upper Endoscopy with swelling - biopsy negative

I went in for my upper endoscopy last week and they found redness and swelling in parts of my esophagus. They sent in my biopsy to have it reviewed, and they all came back negative. It is really frustrating because I had hoped that I would have my answer as to why I am in the discomfort that I am in. For instance, every time I eat I just feel very unwell throughout my body, burning in my throat, chest pain, and other stuff. Overall, the dr thinks it is acid reflux, and I think it is too. However, the medication that I have been on for over a month has not helped at all. Dr. has told me the next step is a an esophageal monometry (which I heard sucks to do). They are testing to see if my two esophagus sphincters are working properly or letting acid up whenever. I am curious to know if anyone has had a similar experience with their endoscopy biopsy being negative, and what they figured out the problem was. Any experiences are greatly appreciated!