Hi, Possible causes for your symptoms are 1) Cardiac arrhythmia (Electrical disturbances in conduction system of heart) possibly supra ventricular tachycardia. 2) Anxiety which may be more likely in your case as mental stress factors are present. Though it needs to be confirmed by evaluation. I will advise you- 1)You should visit emergency care during episode of fast heart beats at that time electrocardiogram (ECG) may give important information. 2) Resting ECG, electrophysiological study of heart, 2DEcho of heart. 3) Tests for kidney function. 4) Thyroid function. Disturbances in menstrual cycle may be due hormonal changes caused due to simple anxiety or there may be thyroid abnormality. I think this may helpful to you. If found helpful vote helpful. Feel free to write back your queries if any.