im a 30-year-old female. my problems started in June of this year. I woke up suddenly in the middle of the night with a racing heartbeat, feeling like i couldn't breathe, hot flashes followed by chills and trembling. since that day, i have been experiencing almost daily episodes of sinus tachycardia. i also feel flushed if my heart reaches over 100 bpm. I haven't felt right since that day. i've had an echocardiogram, event monitor for 21 days, several ekg's, blood work, and a chest xray. these have all been "normal," although the sinus tach did show on the event monitor. my cardiologist doesn't seem to think this is a cardiac problem (this does nothing to calm me down). at this point he wants me to have a 24-hour urine test to check for extra adrenaline. I wasn't too concerned about this until I looked on the Internet what this test was for (pheochromocytoma, carcinoid syndrome). The thought of going for this test is causing me heart palpitations in and of itself, although i know i should. I have a family history of anxiety and also have been taking Xanax .5 mg twice a day since that June episode. in the morning when i get up i feel very jittery, nervous, like im jumping out of my skin. this usually feels less intense after i take the xanax.
I have three questions:
1) in the absence of high blood pressure, can pheochromocytoma still be the cause of my tachycardia?
2) although the Xanax worked well when I first started taking them, I feel that they are less effective now. could the jitter feeling i have in the morning be because I have become used to them and it's kind of like a withdrawal symptom?
3) i would like to stop taking the Xanax every day. how is the best way to stop??
Please help me. it's gotten to the point where I'm convinced im dying. i feel my pulse constantly, am constantly worried about my heart and i dont even want to go to work anymore (which unfortunately I have to do as I have three children.