Hello Good Evening,
This is neither the Heart burn, not it's site, so nothing will happen with antacids.
As the area of abdomen you describe, is called right lumbar region and it contain right kidney
and pain which you have, can be as renal colic
due to renal or upper ureter
Renal colic can be referred to back side to loin of the same side, similar in your case.
To reach final conclusion we should go for:
USG Whole Abdomen.
X-ray Flat Plate Abdomen
After above mentioned investigations, there are strong possibilities to reach the final diagnosis, and right management thereafter.
Dr. Naresh Jain.