That's exactly the same that has ever happened to my husband! 6 years ago, my husband was diagnosed with heart attack. It was in the midsummer. My husband was a engineer and at that time he was in charge of the construction of the stadium. However, after two-month intense outdoor work, he fell ill. For a whole week, he had been feeling extremely tired, thirsty and a strong heartbeat even if it was a slight gesture. No more obvious signs implying the possibility of catching a heart attack. My husband and I just took it as the symptom of heatstroke. However, things got worse several days later. It was then that I realized it was something big and we had to go to the hospital for further examination. Thanks to the doctor, my husband felt much better after one-year consistant treatment. I hope you'll be better off someday in the future.