Yes, a great deal of stress can cause a heart attack, however, if your doctor has assured you that your heart is healthy, then my advice is to take his word. When you feel that your heart is skipping a beat, remember your conversations with your doctor. If you need immediate reassurance, visit the ER, most likely, they will give you something to calm you, and then send you home.
A psychotherapist would probably give you the strength to over come your anxiety attacks on your own.
Also, be sure to ask your health professional about any prescription drugs that can help you overcome your fears.