I have fat malabsorption but rarely get diarrhea. But because i'm not absorbing fat I've had a huge weight loss. But I would think you'd see some obvious evidence of oil in the toilet with floating stool. Your doctor can easily test you for either pancreatic enzyme deficiency or fat malabsorption with stool tests. My vit/min levels were normal at the time I was tested. My weight loss has been a very steady thing however and I can't gain weight at all. In terms of the heartburn, it's possible it's bile reflux vs stomach acid. Good luck at your appointment.