I have been vaccinated, but it's been several months ago, so they wouldn't make an issue out of that. I also had zero side effects after getting the shots, so I'm pretty sure I didn't get myocarditis from the shot.
It's also not exactly excruciating, I barely feel anything, and it's not correlated with exertion. On the contrary, it's more noticable when sitting down than when running or working out. I also don't feel out of breath or anything, but well, sporadic mild chest pains plus palpitations (in the sense that I sometimes feel my heart beating unusually hard, although that might be because I have slight systolic hypertension; but my blood pressure is decent atm) does make me worried about myocarditis a bit, so I should have it checked out. Never had any arrythmia or other heart problems besides the aforementioned hypertension. It's probably just stress, because it has been kinda stressful for me recently. Gotta do more cardio, stop the last bit of smoking I do, and maybe start meditating...