Hi. I'm 17 years old and i've been experiencing something unusaul in my heart. Sometimes my heartbeat gets very high and it won't stop unitil 30 minutes. It just beats really really fast and uncontrollably and my whole chest moves, like my heart is about to come out of my chest. Recently my heart will start to get that feeling, like it's about to beat really fast, but it doesn't and it's like something drops inside my chest and my heartbeat just goes back to normal. Can you tell me if i have some type of heart problem or is this common.