You have kind of answered your own questions really. This all got worse when you stopped birth control pills. You need HRT, specifically you need the oestrogen to calm the anxiety and palpitations down. The health anxiety will melt away with some oestrogen most likely.
I have hurt a rib, might be broken, might be cartilage popped out, so I'm in a lot of pain at the moment and not able to sleep well. As a result I was late applying my oestrogen gel last night. And because that one was late I decided not to apply first thing when I got up today but to do it later. I forgot for hours. My heart had several goes at pounding around lunch time, still didn't twig. Then around 1pm the anxiety and upset feelings started and I remembered. Applied gel and had a rest for half an hour because hurting is tiring, and no more anxiety or pounding heart.
I used to get loads of pounding heart. Different times of day and different activities would cause it. I had no idea it was falling levels of oestrogen.
I'd make yourself that appointment with the GP and ask for some HRT to try. I am really liking the gel and Utrogestan vaginally. You could ask to start with those or ask for a pill form that uses the same progestogen as the BC pill you were recently using because you know you can tolerate that. The beauty of the gel is that you can increase or decrease to find your happy dose.
