I am 50 but always been in good health. I suddenly feel so tired, all the time. My arms and legs are heavy, like I’ve done a workout. My heart feels like it’s racing a lot. I feel breathless doing the smallest thing. If I do housework for a bit I need to lie down. I’ve been to drs (this only started a couple of weeks ago) I’ve had a blood test, normal. I’ve had an ECG, normal. What the heck is it? Never had covid btw, and had a negative lateral flow last week too.