In case this helps someone, GERD can be caused by a bacterial infection by H. Pylori. (According to the Wikipedia, the frequency of infection is at >50% but most people never experience any symptoms.) It was getting worse after eating a lot, eating certain foods , just like for many other commenters here. After getting rid of the infection the symptoms disappeared and never returned.

https://en.m.wikipedia.org/wiki/Helicobacter_pylori

The link to the diseases caused by the bacteria has a crazy discovery story I encourage everyone to read

https://www.nobelprize.org/prizes/medicine/2005/press-releas...