Have you had an echocardiogram? That will detect abnormalities in the heart. More than likely you are just experiencing anxiety. I have a mitral valve prolapse (heart murmur) and once in a while my heart will skip (it feels like a flutter) and then it will reset its rhythm with a strong beat. I don't worry about it anymore, I just go for my checkups to be sure nothing has changed. The echo might put your mind at ease--it did mine. Take care.