Glad you are making progress, wtfbbq. Before all of this I was running 20-25 miles a week, swimming once a week and doing 1 bike workout (usually at the gym). I had been planning a spring marathon and a half-ironman this summer (Both were canceled).
I had most of the classic COVID-like symptoms, starting in late February, but the symptoms were mild and I couldn't get a test. As I started feeling better, I tried running but it caused a relapse of symptoms, especially shortness of breath, lung soreness and chest tightness. Barely been able to run without consequences/symptoms ever since, so I mostly walk at least 1M a day, which has been tolerable.
Because of these issues, I got in to see a doctor in early June. Tested negative for antibodies and my lungs and heart were normal, so my doctor thinks it's a post viral issue and encouraged easing back into exercise but also expect not be back to normal for at least a couple of more months. I've done a couple of 30 minute bike rides since and I did my first 1-mile run in a month a half yesterday. Still getting the symptoms, especially after these workouts or while wearing a mask while grocery shopping, but they aren't as intense or as long lasting, so I appear to be slowing improving.
While maybe it wasn't COVID, I'm also part of a COVID group where there are scores of people with similar stories about symptoms/but negative tests and people who test positive initially but then don't test positive for antibodies. I've also read antibodies can ebb after a couple months (I was tested 3 months later). Some of theories why all this might be is apparently some people's immune systems clear the virus with T-Cells/IgA antibodies without producing much if at all of the IgG antibody (the one typically measured). Regardless, I've gained about 10 pounds and my lungs definitely aren't the same. I want to improve fitness as much as I can, because with no antibodies/weak lungs, I'm probably now at-risk.
Thanks for sharing your story and update and I wish you well.