robin,

Thanks for your posted question.  It's difficult to tell what's causing your symptoms, and the possibilities are many.  I suggest you make an appointment with your physician to ask further questions and examine you.  He might perform other studies like blood work or an electrocardiogram.  With this information, he will have a better idea of what may me the problem.  Most of the possible causes are not serious, but you still need an evaluation by your doctor. 

In the meantime, please review this website and become familiar with the heart, symptoms related to the heart.  This will serve as a good background for your visit with your personal physician.

Thanks.

Martin Cane, M.D.