Do i have heart disease?

Im 15 and vegan. Everytime i play or do a simple excercise my heart races immediatly and i sweat. Im a pretty skinny girl. Each time i stand up i faint and fall down for t seconds then i regain my strength and I get up. ThT happens once every few weeks. Or sometimes twice per week. I get this pain in my chest and... show more Im 15 and vegan. Everytime i play or do a simple excercise my heart races immediatly and i sweat. Im a pretty skinny girl. Each time i stand up i faint and fall down for t seconds then i regain my strength and I get up. ThT happens once every few weeks. Or sometimes twice per week. I get this pain in my chest and back area where it hurts for a few seconds then i stops. Sometimes its so bad i cant inhale cause it gets worse but then it stops. What is this
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