I would recommend having your parents take you to see an electrophysiologist. They are cardiologists who specialize in rhythm disorders. Ask them about wearing a holter monitor. Holters are similar to EKGs but they can be worn under your clothing for 24-48 hours in hopes that they can catch the problem while you are experiencing it. If your symptoms occur very infrequently, then they may give you an event monitor which can be used for a month or more.
Good luck
Your Young ! and Health is good. The Anxiety is a problem for sure, and can cause palpitations to happen , but other things can also cause palps to happen. alot of times EKG and Stress treadmill tests dont always show everything, as maybe at the time you didnt have any palps happen? so tests are normal looking.?
I think the best thing would be to see a Good Cardiologist soon.
and have them test you for this problem. they can treat you on the spot and take care of the problem in most cases.
Just make sure ,you see a real 100% cardiologist and not a Intern learning ... I had one a few years ago.. what a mess he made for me !!
.