Hello. 21 Year Old Female Here. So Starting Last Monday
I would explain as follows:
Welcome to Ask a Doctor service!
I passed carefully through your question and would explain that your symptoms could be related to different possible causes: gastritis, a cardiac issue, or musculoskeletal pain.
I would like to know if you have performed a resting ECG and cardiac enzymes in the ER.
If you have not performed these tests yet, I would recommend performing them.
Is the pain triggered by deep breathing or body movements? This would be indicative of musculoskeletal pain.
Does Tylenol or Ibuprofen relieve your complaints?
This would also be indicative of musculoskeletal pain ( probably local inflammation).
Regarding the increased heart rate, I would agree with your Doctor that it could be related to inflammation/ infection or dehydration.
I would also recommend checking blood pressure values, as low blood pressure could be another sign of dehydration and you may need to take rehydration solutions ( in the drug store).
I remain at your disposal for any further questions whenever you need!