Parasites or POTS?

I am 22 years old from Texas and have been experiencing abnormal symptoms since July where I had to go to the ER because I started to have palpitations, chest pressure, and trouble breathing in class. They did blood work and hooked me up to a machine and everything was fine so they suggested a cardiologist. My symptoms since then include diarrehia or loose stools which I had before the ER incident, I get light headed and dizziness, sleep problems, anxiety type feelings, high blood pressure, most times I eat and dont feel full, gas and bloating, bad gas, palpitations, and sometimes chest pain, I developed TMJ over a year ago, and I find that i constantly itch my nose. It has been a rough 4 months because before all this started I was pretty healthy and worked out everyday. The light headed/dizzines feeling keeps me from going to the gym or doing hard workouts like I used to do. Ive been going to a cardiologisit and all of my tests showed up fine but I was put on a beta blocker. I got off of the beta blocker because I was having bad side effects to it and could not carry on a normal day. I went to a primary care doctor and he gave me 2 capsules to fill for a stool sample, both came back negative for parasites but Ive read that it is sometimes hard to detect for parasites especially if you only go off of 2 stool samples. I was reading another forum and saw a post for POTS and some of those problems match my symptoms. Im not sure if it could be Postural Orthostatic Tachycardia Syndrome (POTS) because I have never heard of it before and do not know how I would have developed that situation.

Like I mentioned earlier, this has been a rough 4 months for me and I just want to go back to normal lifestyle. I still think it is parasites but now im wondering if it could be other things like POTS. I really hope someone can give me some feedback or answers because this is starting to really take a toll on me with depression like feelings. Thanks

Cory