Ok this is just going to be a wall of text but I really don't know who else to ask, everyone around here says It's anxiety..so here's my story.

About 4 months ago..a week after I turned 18 I was sitting on my friends porch and everything was fine. Then I stood up to go to the bathroom..and I felt my stomach tingling and it started going numb. I went to the bathroom walked out and sit down and then my muscles cramped my arms drew up and I couldn't move anything from the waste up. I had slurred speech and no one could understand me. I was rushed to the ER and they ran some tests and blood work and whatnot and found that my pottassium and magnesium levels were dangerously low..and that was the cause of the paralysis. Ever since then I have been having some heart problems..my heart beat is erratic and it speeds up and slows down speeds up slows down. I was pretty athletic and worked out before all this..but I was losing weight pretty rapidly WITH a good appetite. For 4 months I have been in bed because my Cardiologist keeps telling me theres all kinds of different things wrong..he's been wrong a few times already and It's really messed with my nerves and just was a turning point for my life. I had an echo EKG's every heart scan you could have..and the first time everything looked good..maybe a leaky valve. But when I did a walking stress test they said my EF was 46% and my heart was weak. He said I could have cardiomyopathy which I think is a big word for heart disease. I JUST turned 18 and I don't think that even runs through my family so I don't see how I would pick up such a heart condition so early on in my life. It's really scared me and my anxiety is bad but I'm feeling new symptoms on top of what I felt before. I get dizzy..my blood pressure jumps around..my heart rate is now a solid 75-80 at rest when it used to be 55-65. When I stand up and walk around I'm really dizzy and light headed..and I feel like the top of my head is gonna explode. The cardiologist put me on a beta blocker and ever since I started taking it I got worse..but I can't stop taking it because if I miss a pill I just can't deal with the side effects..they are so bad. It's like I'm addicted to them now. Another doctor of mine sent me to an endocrinologist to get my glands checked. He said he's almost certain I have a overactive thyroid..but can it cause everything that's happening to me? That worries me too..what if he's wrong and I do have an incurable heart disease. I can't get the bad thoughts out of my head..even when I'm not thinking about them.. subconsciously I am. I don't sleep much anymore..I get cold and hot at random times..I get random small pressure headaches. I'm real shaky and my nerves are shot. I have 10 days till my test to scan my thyroid..and on November the 10th I go to get the results. But I don't see how I'm gonna make it that long..I feel so bad every second of every day. I'm super short of breath all the time..and I have to take potassium and magnesium daily because I can't keep my levels up. Every other test I did came back good. Every one of them..the only thing was the ejection fraction. I hate taking this beta blocker and I really wanna stop..but when I try to gradually my heart goes crazy. I have energy but I'm not allowed to use it..I'm not allowed to work..swim do anything I used to. I'm stuck in bed..and I really need some help..some answers to calm my nerves. So my questions are this..after reading that (if you read it) does this sound like heart disease? Can that be caused by my thyroid being over/underactive? And what else would cause what I have..normally my blood pressure stays 130-139/60-80. Today it was 105/53. So yeah..some help would be GREATLY appreciated.

*Edit* Some other symptoms I left out:
Random chest pains (that arnt even bad and last 5 seconds)
When i laugh I get light headed real bad.
When my adrenaline starts pumping I get tingly all over
Pains at random parts of my body.
When I'm sleeping and switch positions my heart rate jumps u
My muscles just randomly like..move..or pulsate