I had some pretty severe arrhythmia 2010-2013, and I still get occasional episodes. I can tell you my symptoms are pretty similar to yours although I often feel it more between my shoulders blades, but also above the left breast. Interestingly, I also had a lot of strep throat and canker sores as a kid, and prozac for a while. I don't know if that's relevant or not.
Anyway, I found out that a major trigger of my palpitations was anything containing licorice or anise. I did some research, and there is something contained in them which is known to cause arrhythmia. I found out that it is a common natural flavoring found in flavored coffees and other items which I was consuming a lot. I was also getting too much caffeine at the time. I cut way back on caffeine, avoided anything with licorice or anise, and even unidentified "natural flavors". I started taking supplements to strengthen my heart and circulation, such as vitamin D and magnesium. I have been free of serious episodes for 2 years now, and when I have had them, they can usually be traced back to caffeine consumption creeping up and flavorings.
At their worst, it got so bad that my vision dimmed and my extremities were cold to the touch! I hope you don't let yours get that bad; my best wishes are for your success in fighting this.
Glad to hear you are getting checked for auto immunity issues. When you say your heart speeds up have you checked how fast? If you can see if you can note the speed it is. Some of the meds you are taking can affect the heart especially the allergy meds. Caffeine as the previous poster mentioned is also a big trigger as well stress and anxiety. Stomach issues too. In any event, I would push to see a cardiologist just to make sure all is healthy with the heart. Odds are something outside the heart is adding stress to it but best to get it checked out and know for sure the heart is structurally fine. Best of luck sorting it all out and keep us posted on how you are doing.
I'm still experiencing the chest pain though it hasn't got any worse. It's difficult to get a read on my heart speed when I experience the palpitations because it jumps around a lot, sometimes one beat a second, sometimes two.
I got the blood work back and I do not have an auto immune disease (no sign of rheumatoid factor or inflammation). I'm not much of a caffeine drinker- sometimes I drink tea (usually green) but not more than one cup a day. I looked up licorice and anise and it doesn't seem like I've had anything containing either of those recently. My digestion has been fine.
As for the allergy meds, I've been taking the lowest dose of singulair for the past 10 yrs and haven't had any issues in the past. I was on symbicort briefly about half a yr ago but made me really shaky and my heart rate was over 100 bpm (normally it's been 65), so I was switched to flovent which doesn't have the beta agonist and the issue went away. I haven't taken my albuterol (proair) in about a week.
Did they check for Lyme disease? You can pick up ticks just working in the garden. Darn things are a scourge.....
I was thinking the same as Tom. Lyme disease can cause all or most of your symptoms and you may not even be aware of the tick bite. If they haven't already checked you for that I would request that they do. I was diagnosed with it 20 years ago and have never been sicker in my life.