Irregular and fast heartbeats, sometimes accompanied by faintness - HELP

Hello everyone! I really need your help figuring this one out.
I am 21 years old, vegan and have low blood pressure normally, but I would say I am pretty healthy.

Let me start out with I've had irregular heartbeats for a few years now, but they are not painful (only Very uncomfortable!) and only come maybe once a month, so I didn't think much of it. I have noticed that these past few months I've gotten them a week before my painful periods (hormones?)
Recently I decided I ought to get it looked over.

Jan 16 I was sitting at my computer, while my stomach made some noises and movement (my stomach has not been fully right as I had some type of stomach bug / food poisoning a week before, and then started burping everytime I eat, even from drinking water), and instantly I got a flash of lightheadedness and my heart started racing. I thought my heart stopped for a moment so I couldn't calm myself down the whole night.

The next day I went to the doctor. She did an EKG and said my heart just had a little bit of sinus arrythmia (also not normal for me on a good day), and we did blood work. She said my heart is healthy and the blood test shows I'm healthy besides a low vitamin D level (at 22). No other deficiencies.

However it kept happening throughout the week, my heart would race from literally Nothing. They put a 24hr heart monitor and found that my heart went into tachycardia 26 times, but they don't know what triggered it. I could be sitting down in class and my heart will speed up to 85-95bpm. The doctor wanted to put me on a beta blocker, but I found other natural beta blockers that don't have bad side effects like medicine does (bananas, chamomile, pomegranate, etc).

And still it continued. My chest has felt very right and my breathing doesn't feel as good, like as though my esophagus is inflamed and a heavy weight is on my chest. My boobs have been a bit more sore lately. I would be sitting at my desk and suddenly a flash of lightheadedness followed by my heart racing again and me feeling shaky and burping from anything, even if I was completely calm before hand. It finally happened again last week where my heart stayed at around 95bpm (my normal is 60) and I felt very shaky, sort of dizzy, distant, and lightheaded. By this time I was nearly only eating a raw diet to help cleans my system, and I wasn't even eating much that day so I don't think food allergies of any kind triggered it. And after it persisted for a few hours and I couldn't really get my heart to normal or remove the symptoms of faint headed, shakiness, and oddly burping (no matter how deeply and calmly I breathed in), I went to the ER.
When they took my blood they said my potassium was the slightest bit low at 3.5 this time, but other than that I was fine. They called it off as anxiety, but I have no history of anxiety, nor is it in my genes, not have I been overly stressed. Anxiety doesn't describe the weird burping or my hands turning numb that night (when I was Not hyperventilatingt), the irregular heartbeats in my sleep, etc.

I just want answers. I have been taking some wonderful natural supplements as specified by my aunt who is a nutritionist. I am taking L-Carnitine, Hawthorn Berry and Ubiquinol CoQ10 (all good for the heart), my normal megafoods multivitamin for womens, an herbal infection killer, digest gold (enzymes to help break down food), probiotics, and glutamine (to help stomach ulcers if it happens to be why my stomach has been acting up in connection with my heart). These plus chamomile bananas and pomegranate juice has wonderfully helped and quieted down my heart so it's not thumping out of my chest, but still the sinus arrhythmia and random tachycardia or PVCs exist.
Yesterday I felt vertigo as though I was sick but with no other symptoms (no soar throat, no headach, nothing), once in the shower, the other in church.

Where is this all coming from? Any suggestions please:(( Tweet