Trouble from above. Some palpitations stem from premature contractions of the heart's upper chambers (atria). When the atria contract a fraction of a second earlier than they should, they rest an instant longer afterward to get back to their usual rhythm. This feels like a skipped beat and is often followed by a noticeably forceful contraction as the lower chambers (ventricles) clear out the extra blood they accumulated during the pause. These premature beats are almost always benign, meaning they aren't life-threatening or the sign of a heart attack in the making.
You probably know you do (though you may not). Either way, I am sure you can't hide it from yourself forever. Am I right? And you will not be able to hide it from your friends forever either. There will be times when everybody’s sharing secrets, or maybe you'll just tell your best friends. Well, if I were you, I would tell my friends about it, because I am sure they would completely support you. Or at least, they would intend to. Because, in reality, when your crush is around, their idea of support may go something like shouting, “Oh my God, somebody is approaching!” and start to tease you—and the teasing is likely to persist for the whole day. While you will be the only trying to act like a sane person, standing like a stone and smiling in front of him/her. The one thing in your mind will be, “I’m going to kill you guys!” It's the sad reality, but that’s the character of true friends (mostly). Experienced it? Devastating, right? That’s okay. At least you have your supporters.