what are they?

a while ago, I noticed that my heart would start racing or beating really hard and loud, I'm not sure which, when it was least expected..
i'd be sitting there watching TV or ready to go to sleep and my heart seemed to go nuts..
i don't think i ever experienced pain except once..

so i went to the doctor, he hooked me up to something really scary that ended up not hurting, and told me there was nothing wrong with me. He said it was prob. too much caffeine.. i know it couldn't be true since i rarely drink coffee/soda/tea.. or caffeine, but i ignored it cuz he said it was nothing serious or having to do with my heart..

i went to another doctor two days ago (for a different reason) and she said she thinks i have panic attacks..
how weird is that? i never imagined..
she refered me to a mental hospital or something like that.. but i really don't think i have that.. but who knows? i'm not a doctor.. yet... lol

anyway, so does anyone have them or know what it's like? and is it curable?

thanks =)