I remember going for a shop the day my 10 day isolation finished and it was a massive struggle. I collapsed on the sofa as soon as ai got in the door - body was running on fumes. It took a few months to get stamina levels back so hopefully you’ll get there soon.
The anxiety could be you subconsciously worrying / overthinking everything you’re suffering is attributed to the COVID. I seemed to have a constant cold that I couldn’t shift and was unsure whether it was COVID hangover, just a low immunity after COVID or possibly a bit of both