neurocardiogenic syncope or POTS? plz help

Hello. I'm a 20 year old female at age 18 I became very ill with constant lightheaded and dizzy episodes. I was told upon two E.R visits that I had orthostatic hypotension. I followed up with a cardio and was told I had neurocardiogenic syncope. I was so ill that I could not get out of bed because I would always be on the verge of fanting. I had a tilt table where my heart rate went up to 180. There was not a moment I did not feel sick. I was then sent to a electrophisiologyst (SP) who told me I  had innapropriate Sinus tachycardia and Postural orthostatic tachycardia syndrome. By this time my heart rate was constantly in the 150-180's even with lying down. My blood pressure was no getting high with sitting/standing and low with lying down. My question is why would my blood presure always be low and no be getting high. Nothing has changed, I am not on medications because they made me sicker, I am unacctive because I am too ill to stand for more than a few minutes and I always drank lots of water and gatoraid. I did increase my salt intake. Do you agree that this is in fact POTS and not something more serious or dangerous. My EP told me not to worry about a heart attac or anything of that sort that this was not a dangerous condition, just annoying. I still am worried however,  My heart rate is constantly rapid for over a year and a half now.