Don't feel bad about going to the ER, in a way those can turn out to be positive reminders of just how healthy you are. Doctors and nurses are trained medical professionals. They strive to find anomolies and will work their hardest to find resolution. They know the signs and symptoms, you sometimes have to have a bit of faith, but trust in their educated judgment that you are in good health.
I've had multiple anxiety attacks over the past year and have been to the ER 5-6 times myself. I hope I won't go again, but never underestimate the power of anxiety. Even though I haven't had to seek medical assistance, there are days I've had to cancel plans, and just spend the day on the bed or couch resting because I could just feel my anxiety being sky high. I'm also the type to -never- call in to work, so i work with high anxiety too, which isn't a good thing.
It's all about knowing your body, and working with the signals your mind is sending out to determine the real from the fake. It's not easy in the slightest, and takes multiple bad attacks before you can breathe and confirm to yourself that it's just anxiety, and not a heart attack. Anxiety is a sinister and twisted demon, it loves to imitate various ailments and seems to know when/where to strike us.
Stay strong my friend, and hope there are better and sunnier days ahead.