10yr old f. W/severe abdominal pain below sternum at night. No fever, pain is like squeezing hard, antacids dull the pain. Wakes up crying. 3 days?

Endoscopy. See a G.I. Doctor to get an endoscopy. Could be gastritis, an early ulcer or an esophageal stricture. If any of the above, it is likely caused by an infection with a bacteria called helicobacter pylori and can be treated with antibiotics and acid blocking medications. When laying flat in bed at night, the acid from the stomach can come up into the esophagus causing severe chest pain.
Reflux/bone/heart. The 3 things that produce pain in that location start with ge reflux, or heartburn that can certainly happen at that age & respond some to antacids. Pain in the rib cage in the breast bone would be #2 & a rare event would be a pericarditis or inflammation around the heart muscle. This can be sorted out by exam & tests.If heart burn, diet changes & rx meds can help.