Some advice from someone who does this professionally:

As several have said, you need to see a physician. You may have experienced sinus tachycardia, supraventricular tachycardia, WPW, atrial fibrillation, atrial flutter or some other rhythm. You won't find out on the internet. If you are currently having symptoms, go to the ER. If it's something you had a few days ago, follow up with your family doctor soon. You may well be referred to a cardiologist. You may end up with a Holter monitor or an event monitor after having an ECG and some basic lab work. You may need a stress test and an echocardiogram.

Good luck to you.