hello, today, i was doing kickboxing, nothing un-normal, i do it twice a week, but tonights lesson wasnt the same, i did 5 minutes of exercise and i felt very faint, very quick heartbeat, and terrible chest pain, then, my heart just completely stopped beating, i collapsed, but 10 mins later, recovered and carried on with kickboxing, after the one hour lesson, i was violently sick and passed out on the way home in the car (i wasnt driving). i just dont understand why this was, its never happened before? i'm 13 if this helps?