Stool that is pale or grey may be caused by insufficient bile output due to conditions such as cholecystitis, gallstones, biliary dyskinesia, giardia parasitic infection, hepatitis, chronic
pancreatitis, or cirrhosis. Bile salts from the liver give
stool its brownish color. If there is decreased bile output, stool is much lighter in color.
Reflux can be a symptom of some of these as well.
Personal experience: I was getting the same thing, heartburn, pale stools, etc.