there is no much clue from your history other than heartburn
.is there any history of vomiting out of blood,black tarry stool,excessive menstrual bleeding
,fever,bony pain or rash.due to frequent heartburn,the most possibility is bleeding peptic ulcer
or GERD.at first you will consult with a gastroenterologist for upper GIT endoscopy.if it is normal then you will consult with a hematologist
for further evaluation of anaemia.