First, chest pain has nothing to do with whether you're having an anxiety attack or not -- people's symptoms vary considerably. Listening to doctors about anxiety can be a rough patch. So it seems to me, as a long-time anxiety sufferer, that you have two things you need to do: find a better doctor who can find out why you fainted and deal with it -- if it's low blood pressure, work on that. If it was altitude and dehydration, or low blood sugar, which is what it sounds like, you need to eat better to work on this. You don't describe your physical fitness level, but if you're not exercising it might be time to do so. Exercise and meditation are two things that can regulate your blood flow and make sure nutrients are moving around and your blood is moving around so you don't end up feeling faint. Second, what you're suffering now I think you've accurately described -- you're afraid this is going to happen again and you're developing a chronic anxiety problem. I don't know you're age, but it could be you were on the way to developing some anxiety problem anyway, but you want to get on top of it quickly. There's no guaranteed way to do this, but before avoidance becomes normal for you, which will make the problem worse, I'd get to a psychologist who specializes in anxiety treatment and knows relaxation techniques that can get you past this kind of thinking.