Hi, Heart palpitations could be due to anxiety, stress,anemia,gastric reflux or may be ectopic beats,SVT. In healthy individuals, it is mostly of anxiety or stress but if you have shortness of breath and headache,then you must evaluate for premature atrial or ventricular contractions,paroxysmal supra ventricular tachycardia, atrial fibrillation etc. The above heart diseases have many other symptoms apart from palpitations and SOB but they some times start with this symptoms. You can undergo ECG,holter monitoring ( 24 hr heart activity) ,TMT if no contraindications, or 2D echo to rule our heart problem. You must consult your physician if facing this problem since long time. You can continue with tab.lexapro,its good drug for anxiety.