The colour of your stool depends on your diet you have taken.Passing greyish green stool
is not a disease.
is treatable.Now,good drugs have come which cures GERD.
Please avoid spicy foods.
Nice to hear that your Ultrasound
abdomen is normal.
Please consult your Gastroenterologist and get proper prescription.
Stop worrying as it may aggravate GERD.
Wish you good health.