thank you for your querychest pain
can be due to numerous reasons.a few of them are
1.angina or cardiac pain
2. Chest muscle injury
3. muscle spasm due to excercise
4. Peptic ulcer
5. Pain from the digestive tract, such as esophageal reflux
6.gas due to constipation
from abdomen due to irritation of phrenic nerve
some times MI cant be diagnosed by one ECG alone.it is called as non-STEMI.
i would ask you to keep your BP under check and also start with calcium tablets as in some cases this sign is due to an underlying calcium disorder.
also avoid stressful environment and have regular sleep shcedule.
wishing you good health