Buy a lottery ticket. Your chance of getting more than four numbers on it are hundreds if not thousands of time more likely than you having Long QT, and tens if not hundreds of thousands of times more likely than Long QT killing you.
I came out of hiding to make this post because you sound precisely like I did in 2009, worrying about exactly the same thing as I did. I, too, had a lot going on that coincided with my health anxiety. Eventually, nothing but everyone around me being right came of my Long QT worry. In these last four years my parents, aunts, uncles, and cousins have all encountered health problems and my fiancée had major surgery (at our young age, nonetheless) and is still recovering. I seem to be the only one who's healthy!
However it is inevitable that I will make it through life without encountering some serious health problem; nobody lives as long and as well as we humans and gets to the end unscathed. I've learned that my heart will palpitate occasionally, that my lungs will feel tight sometimes, and that it doesn't mean I'm in danger. Those things and so much more happen to everybody else, too, I've learned. And yet late at night when my mind wanders I find myself returning to these Health Anxiety forums, which I keep as a little bookmark on my phone, and reading everyone else's posts and worries somehow keeps me sane, sane enough to help my fiancée recuperate or be the second person at my father in-law's cardiologist check-ups; these forums keep me sane enough to fall asleep with my phone in my hands while I read.
I'm not really sure how I've gotten better. However, I can tell you that in four years I've seen a lot of usernames come and go on these forums; somehow many of us seem to let go of the crippling focus we've had on our health, we let go of it or it lets go of us. You, too, will have that happen as the odds are in its favor. Unless that lottery ticket turns out to be a winner, of course!
Keep reading the forums, brother, you'll want to get out of bed soon enough.