Yo, I've experienced this with illness that took a long time to shake off. Here's what helped for me:
- sunlight
- gentle exercise
- breathwork

I couldn't work out properly, so just went for walks to get some fresh air and sunlight, and did a bit of yoga.

Breathwork (e.g. Wim Hof) was good, but I took it easy. As I started improving, I threw in a bit of cold exposure.

Once you start improving, don't make the same mistake I did of pushing yourself too hard, too early. After a long illness you need to build back slowly and continue to prioritise rest and recovery. 

 I sure appreciate it.  What makes it hard is the inability to breathe without hacking up a lung. 
It makes everything strenuous. 
I get so out of breath so quickly. 
I'm still trying to be outside as much as I can. I have extremely low BP and energy,  so I do have to be cautious with not falling as I'm constantly light headed. 
Sun is so necessary!!!
🤗