Do I have a heart problem?

I'm 18 years old, about 170 lbs, in relatively good shape. I'm able to jog at least a half hour to an hour at a time. Every since I can remember though, I've gotten some weird things going on with my heart. I don't know if it's a defect or what, but what happens is that I'll just be sitting there, totally relaxed even, and my heart rate will just shoot up. My heart will start pounding really hard and make it hard to do anything physical besides walking around. It doesn't feel normal. It feels wrong. I've been able to sort of control it through relaxing and doing breathing exercises when this happens, but I just don't know why it happens. I've had my heart checked with a stethoscope and the doctor said that it sounds totally normal. I'm wondering if it might be related to anxiety, or might be some kind of panic attack, or maybe my brain decides it needs more oxygen, I don't know. Please help. Thanks so much for taking time to read my question.

If you are getting these irregularities often you may need to be placed on a Holter monitor which will monitor your heart over a period of time, usually 24 hours. Your heart could be going into an irregular rhythm for a bit and then going back to normal and more than likely when the doctor listened for that short period of time, your heart was normal. It could very well be associated with stress or panic attacks, but I would tell the doc what is going on, it may be nothing, but it may need to be evaluated more thoroughly. Better to be safe than sorry. Good luck!

you could have an artery that suddenly shuts up when you become stressed.

arrrghh you ........ sorry but that is almost 100 percent exact to what i am expereinceing doctors said that nothing was wrong and i just recently got this a year ago or so and im only 19 it pisses me off , the doctor said it was all in my head and asked me if i was doing DRUGS man i was so pissed off ,
though i stumbled upon a discovery , i smoke my self , cigerettes , as you know people get addicted , so i quit smoking for a while and the palpitations that i was having got worse and more frequent when i smoked they became regular, though i cant ask you anything right now lol but when i eat a meal that is not veges or something that is not rich i feel fine but when i eat pizza and pastas etc my heart starts beating like i just ran the mile ,
i also have expirenced random thuds in my heart and weird beats that feel like my heart was half empty when it beat
though i am under insane stress my freind crashed his car into my garage my parents are deaf they need my help constantly and i cant let them down etc.
if you end up finding something out id be gald to hear the details