Oh, yes I do have same symptoms. I remind myself that exhaustion is a symptom of PD. The heaviness in the legs is the worst. My shortness of breath may be because I have a large hernia which is compressing a lobe of one lung per MRI and chest x-ray. Also spinal compression can cause these symptoms.
My legs feel so heavy and are painful on weight bearing.

You may want to revisit these issues with a different doctor, like a rheumatologist. They order blood tests that are more and unusual than another doctor might order. I am not a doctor, but I know enough that checking heart and lungs may not be sufficient to know what the cause.

The legs could be PD related. I need to lather myself in lidocaine cream 5% topical; it helps a little for awhile.
Wondering if you had a definitive exam with the right specialists?

Stethoscope listening by doctor is very superficial. Just think about what was actually done. I imagine your heart and lungs are fine, but your symptoms go beyond the heart and lungs.

I hope you get the relief and answers you deserve.

To update my answer from before, I went to a physiotherapist to do more stamina training. He thought I did well. I also went to a pulmonologist who tested my lung capacity, said it was fine, and wanted me to do a sleep study. I don't think there's anything the matter with my sleeping, and I would refuse to use a CPAP, so I just stopped the investigation I've asked my neurologist multiple times if it could be related to PD, but she doesn't really answer. Masks with COVID definitely made it worse.

Could this be a sign of an allergy?

I go up 1 flight of stairs and my legs weigh 10,000 lbs , then I get wheezy (not from the Jefferson’s😜)