Welcome to HCM
We understand your concerns
I went through your problem description. You should not worry unnecessarily. Chest pain
below the rib center joint might be due to acidity or muscular cramp. You are just 18 and you should not have any heart problem. Acid reflux
presses the diaphragm upwards and there might be pain around the area.
For confirmation, please visit a general physician.
Hope this clarifies your doubt. Available for further clarification.