Symp: feel like i'm going to pass out. heart starts beating fast, lightheaded and can't catch my breath.happens with and without any physical activity?

Check blood pressure: These symptoms are fairly common in young women. Does this happen only when you're standing? If so, could be a drop in your blood pressure or something such as pots syndrome. If it happens all the time, could be anxiety or panic attacks. Could also be a problem with the lungs, but i think this is less likely. Best to see your doctor to have it checked.