I’ve had similar issues following a surgery (Whipple procedure) to remove a neuroendocrine tumor (NET) from my small intestine. The tumor was a gastrinoma, meaning that it produced the hormone gastrin which triggers the secretion of gastric acid. This stomach acid has the effect of breaking down pancreatic enzymes which aid in digestion. This lack of enzymes results in food not properly being digested in the small intestine thereby feeding the microbiome in the large intestines. This leads to severe gas and diarrhea. The volume of diarrhea is the result of your body drawing out water to manage the undigested food. My symptoms continue which suggest that there are other gastrinomas that are still present that were not removed during the surgery or have developed since the surgery.

I share this only as a suggestion to rule out the presence of a gastinoma tumor. The change in symptoms is concerning and is somewhat similar to my symptoms (though my symptoms are more sporadic). Best of luck and Godspeed to a resolution to your symptoms!