I doubt seriously if you have any form of heart disease at this point, it would be extremely rare for some one as you describe. See the cardiologist for peace of mind, most likely anxiety.
You do not mention a family history of heart disease or problems of blood pressure or obesity. Taken in the context of your youth and the number of tests you have already had, then the lightheadedness, shortness of breath, and the kind of chest pain you describe are absolutely *not* diagnostic hallmarks of heart disease for you. They are, however, characteristic of anxiety.
By all means, see a cardiologist. But if he/she tells you that you're OK in the heart department, you are. You might, however, benefit from a little counseling to help you with anxiety and stress.