Hello. Welcome to hcm. Gerd is a disorder which causes reflux of gastric contents leading to pain,burning sensation in chest. Lower sphincter is lax and so part of stomach has also entered to chest causing hiatus hernia. It is very unusual to find fecal matter in mouth. It could be two reasons. You might have a pouch in throat where is food is getting collected called zenkers diverticulum or you have a abnormal connection between stomach and colon. I advice you to undergo barium meal test and ct scan abdomen to find out abnormal connection in your colon and get it corrected surgically. All the best