Thanks for writing your query.
Colour of the stool also depends upon the food eaten.
Dark tanned stool can also be due to bleeding in the gastrointestinal tract.
After reading your post, I would suggest that you should get your stool examined for occult blood in addition to routine and microscopic examination.
You can take an antacid
40mg once a day before meals.
Further medical management can be planned according to the reports of the above mentioned investigation.
I hope this is helpful to you.