This sounds like Paroxysmal Supra Ventricular Tachycardia - an irregularly fast heart rate that originates above the ventricles in the atria. Paroxysmal supraventricular tachycardia (PSVT) is episodic, with an abrupt onset and termination. Manifestations of SVT are quite variable; patients may be asymptomatic or they may present with minor palpitations or more severe symptoms. Anxiety can trigger episodes of PSVT, as well as stress, all of the events that you listed above probably initiated it. If it causes severe symptoms, a doctor might have to prescribe Beta Blockers to control the rate and also to help prevent future attacks. This is a very common disorder present in millions of Americans and is very rarely life threatening, the worst type is WPW, in which an alternate path leads to the ventricles which could cause an abnormal ventricular rhythm which could be dangerous. You should get an ECG done to rule this out, as the signature finding is an upslurred upstroke in the QRS complex.