Having caught it twice, and being diagnosed with 'long covid' after the first time, the post illness effects can just drag on and on.
The only advice I am qualified to give is to fight the malaise, fight the ongoing symptoms, and (if you needed to, lose weight) get as fit as you can.
You'll want to give up every time you exercise, even starting with the very basics like walking; it will be hell, but bit by bit, if you keep fighting you'll fully recover. But it is tough, really, really tough.
Seriously, fight the after effects, put yourselves through it and get fit. It worked for me and it might work for you. You just cannot give into the symptoms, no matter how bad they can make it feel whilst you're doing it.
You have to help yourself, there are simply no magic medical drugs/treatments that can do it for you.