@Sirtruckdriver If you get worse by physical activity, please be very careful. If it is a temporary thing (like an infection) then you can get help. I don't know anything about heart problems, so I have no advice on that. If it is a more long lasting problem, it might, (MIGHT; not giving any remote diagnosis ofc) be ME/CFS. I have had it for 21 years, and unlike most chronic problems, exertion does not help. Or it must be very carefully paced. And most doctors know NOTHING about it.