I had asked for some additional information and have not heard back.
If the gastroscopies did not show any evidence of ongoing reflux, then it may help to perform a more sensitive test, which is a 24-hour esophageal pH probe, which can quantify the frequency and severity of reflux.
An esophageal manometry test can be done to assess the muscular activity of the esophagus, particularly looking for times that the esophagus may spasm or when the muscles are not coordinated well, call dysmotility.
If there is ongoing reflux despite the PPIs, then it may help to augment the PPI with a different medicine, such as an H2 blocker, e.g., ranitidine. The PPIs are typically stronger than the ranitidine, but the ranitidine can be used to augment the PPI.
Altering the diet can help some people, but many people with reflux find that it does not make much difference. If you find that it helps you, it is certainly fine to continue. Another lifestyle intervention that may help is the placement of blocks under the feet at the head of the bed. The blocks should be about 6 inches/15 cm tall, so that you are sleeping at an angle, which can help keep gravity on your side while asleep. It is also important to note that sleeping on extra pillows does not work as well, as it makes you bend at the waist. It is better to be straight, but at an angle.
In someone with persistent reflux despite multiple medicines, another option to consider would be surgery to prevent the acid reflux, which involves a procedure called a fundoplication, in which a portion of the stomach is used to wrap around the lower esophagus. We do nt need to do this procedure anywhere near as often as we once did, because the PPIs are generally very good medicines, but there still are some people with stubborn reflux that require surgery.
If I can provide any additional information, please let me know.