Heart Problem

I am a 23 year Asian female who doesn't have any major health conditions, I do have minor asthma and allergies but that is about it. When I am 5 years old I fainted prior to getting chicken pox and a year later I fainted again with no explanation and then again the year afterwards, up until I was in junior high school I fainted about once a year. My mom brought me to a doctor but they couldnt find a reason, i also went to a brain specialist but they couldnt find the reason behind this either. then in high school i fainted again and since i was older i took notice of the symptoms before the fainting happened. i was standing in the train in one position but not for long, maybe about 15 minutes, i would start to get stomach cramps then my vision would get staticy like in a television with no connection then i would feel like i have to sit down and at that point i would pass out. Recently I have noticed that my heart is always above 100 but i have a normal BP. I wanted to know what i have.