The esophagus contracts to push food down into the stomach. The test will check the strength of the esophagus contractions, and the tightness of the value at the bottom into the stomach.
Yours is weak at the bottom, so not contracting as hard as in a normal person, which is why some stomach contents may come up into the esophagus and its hard to get them back down because your esophagus cant 'push' them back in very hard.
The reflux test just tests for presence of acid below a certain pH, if it was normal it means they didnt detect a significant amount, but often people with reflux symptoms get a "normal" pH test result
GERD, Anxiety, Depression, Rolling Hiatus Hernia, Esophageal Hypersensitivity