It cant explode. It can rupture, fibrilate, have heart attack, angina pectoris, many things... But none of them is that scary. All fixable issues with nice team of doctors. Its hard for person to get any heart issues, unless person got it with birth, or if person eats unhealthy food. Your fear is anxiety, but it may be a good kind of it. Maybe it can push you to eat healthier and work out when you can. If you start doing that, i can feel free to assure you, that you will minimize the risk of any heart related issue to minimum.
I dont know what to say anymore. Hope i helped at least a bit