Sorry that you are going thru all of this....it sounds like you are way tooooo young for all of this but maybe you are going to get it all out of the way now and will zero health problems later....the thing that is throwing a red flag for me here is you did not identify your doc as a heart doc and i hope she is one.....as far as your mom being a paramedic that is great because she does have some inside medical info however that is about as far as it goes...anyone could say "it sounds like" or "looks like" but the only true way to really know is to see out a professional opinion with a heart doc NOT a generally family practioner....heart docs only know the heart...you could have experienced anything from a fib, to tach, to contractions to just about anything. You are on ALOT of meds and you don't know which ones are conter productive to your health and each other when combined that is why i am encouraging you strongly to get a work up from a heart doc. No doubt rapid weight loss has been attributed to a racing heart because of the stress it puts on the body and i think losing 10 pounds a week puts you in that catagory. Did the doc say why you had lost that much weight that fast? The stimulants on top of the weight loss is a big no no in anyones book. It is your body and you need to get pro active w. dealing w. everything that is going on with you. Any of us can weigh in on what is going on w. you but you have to remember as Jerry always says...we only share our own experiences and we are not doctors or here as doctors in some cases. Seriously consider seeing a heart doc and make a list of all of the meds you are on to go over it w. him/her. Your pulse rate is not out of control (yet) and for some of us we have experienced our pulse rates going into the 300's but it is just as scary in the 100's mid and upper as the 300's. Get a professional opinion is my weigh in from a specialist and good luck and let us know what happens....
My first thought (due to weight loss, tachycardia, palpitations) is possibly something wrong with your thyroid levels. Your heart symptoms are easy to describe, it's sinus tachycardia with PACs or PVCs. (if you had an ectopic tachycardia, you wouldn't feel skipped beats, and the heart rate would likely be higher). I doubt anything is wrong with your heart, but it is very important that you see a doctor as soon as you can, to find out what is affecting your heart (causing palpitations and elevated heart rate).
I would say this seems like an endocrine problem, but of course, I'm just a layman and cannot tell exactly. The chance this is cardiac related is in my opinion very slim, though.
See a doctor and get thyroid and a couple of other tests done. No need to keep such problems untreated.