I am sixteen and one day at football practice my heart seemed to beat way harder than normal, i could feel it through my whole body and when i felt my chest i could feel my heart beat way more than ever, and i also had chest discomfort and anxiety, ever since then my heart seems to beat harder all the time, and after exercise it takes longer to calm down, i will also get random chest discomforts on certain days,my EKG, holter moniter, and event moniter results have came back normal, but months after that day at practice my heart continues to beat hard, and when i feel my friends hearts through their chests i can barely feel theirs beat,is there anything that could cause this change, because my heart never did that before.