hey, i am 13 years old, i am quite healthy, i don't smoke or do anything bad, i never have. before i was born my mum had a x ray of me, and i had a shadow over my heart, they got it tested to see if i was a downsydrome baby, i wasn't. I frequently get these horrible pains in my heart that last 10 seconds, it's a huge thump that hits my lungs, and i let out a gasp for air, i am so worried what this could be :'( Please help me, Farrah x