I'm in the US, so this advice is only applicable there, but LabCorp will test your blood for you without a doctor's note. I had to route around my doctor because I caught covid in the initial wave and no one knew what was going on. Your doctor may be able to help you more these days. Anyway, so I got my blood tested for all sorts of stuff, fixed deficiencies that came up, then leaned heavily on specialists to get medication to fix my symptoms. Beta blockers/other for my heart palpitations/other issues from a cardiologist, various inhalers for my lung issues from a pulmonologist, a whole slew of medications and treatments from a psychiatrist. And so much help from my friends. At the worst of it, it was exhausting walking from my bedroom to the kitchen, and I live in a small apartment. It did take years, but eventually I got there.

Learning to never push myself, because that would cause me to relapse and spend a week in bed. They have a name for it now, but that's the biggest thing that helped, really.

Hope you get a full recovery soon!