I'm a 21 year old female and was recently diagnosed with Postural Orthostatic Tachycardia Syndrome (POTS). It's where your heart races when you stand and your blood pressure decreases. I've been on proponalol 70 mgs everyday for the past two months and i'm starting to feel really good again. But i have this constant nagging that something else if wrong with my heart. I have these random terrible pains in the left side of my chest, i got one so badly on the left side of my sternum the other day i almost went to the ER, the other pain is by my nipple on the left side of my breast and only hurts when i stood (just one day) and i took one step and had this bad pain in my left shoulder. (i've also been known to have awful back problems with degenerative disc disease and hierniations sp?), i also get pain above my left breast like near my collar bone and in my arm pit. What really scares me is the odd pain down my arm. It's sporadic but sometimes it goes from my armpit to elbow, and sometimes the back of my biceps to my elbow. A lot of the times the pain only happens when I'm walking and I don't know if i'm out of breath or not. I have asthma so its difficult to breathe sometimes but i have no problem talking and i'm not breathing heavily when I get this pain. (I've also been diagnosed with swelling between the ribs). Another concern of mine is this odd feeling of fullness i get in my chest. It stems from my stomach and like spreads up into my chest and feels like a fist is gripping my esophagus. I've noticed recently i've had acid reflux terribly where my throat actually gurgles and sometimes food comes back into my mouth. So i don't know if that's GERD or heart disease. I've had two EKGs when my heart was really fast (150-160) before my POTs was diagnosed and my doctor said it was like a stress test and my heart was fine just ridiculously fast. I've also had a full echocardiogram back in September and a limited one just in March, they said everything was fine except i had a low normal ejection fraction of 52. (they thought this was related to my heart rate being so high constantly and I had lost 20 pounds so my body was struggling) Also, i had an event monitor which recorded tachycardia back in September (before the pains) and i had a halter monitor in March (before these odd sensations). My question is am i just being too crazy and worried about my heart? Do these symptoms seem cardiac related or related to other things? I also think my cholesterol was perfectly fine, but i'm afraid to exert myself because these odd pains keep coming back. The one i had today only went away when I sat down it was like this weird dull pain above my left breast almost parallel with my shoulder.