It's not simply a matter of posture. Also, while I can only guess it's nothing serious, you just said that you're experiencing some of the signs/symptoms of a heart attack. My best guess is that you would benefit most by seeing a chiropractor to address your structure.
Yoga and meditation are your next best bets. If you experience inflammation then you can reduce symptoms with supplements or dietary changes (i.e, turmeric, omega 3, sour cherry, etc.).
It doesn't make much sense to suffer needlessly. If you can resolve your problem yourself within 15 minutes, that's great. If you feel better tomorrow, that's great. But if you have persistent issues then you should probably just take what I said into full consideration and make a lasting change that empowers you to take charge of your body and how you feel.