You sound as if you had some type of arrhythmia
and you need to see a doctor asap. Even if it is fine when you see the doctor, give him your symptoms and he may want you to see a cardiologist and maybe have a stress test
to see what the heart does under a controlled stress.It could be atrial or ventricular problems meaning the upper chambers or the lower chambers, either way it is not normal and not good to let it go on. Please make an appt asap or talk to the MD and tell him about it and he may want you to come into the emergency room to be evaluated. I cannot stress enough how dangerous this isand how important to do something about it asap.