Hello~Have you had an echocardiogram? This is a more thorough exam of the heart, valves and blood flow. If that comes back normal, then I would see a chiropractor, you may have misplaced vertebrae in your upper back.
Also, start taking a Vitamin/mineral supplement, making sure you are getting enough Vitamin D, it is not healthy to be low in it as it helps metabolize calcium and magnesium, both are heart minerals.