I am sorry you are having problems. This sounds nerve related. (I am not a doctor.)Nerves regenerate slowly.
You mention PT, have you tried some other massage type therapies? Active Release Therapy? Myofasial massage? Perhaps if a nerve is entrapped, they would help. Dry needling? Acupuncture? I don't have personal experience with these last two, but friends who have nerve issues have enjoyed relief after these.
Could it be related to swelling? Something swells and then the nerve is pinched? Since it happens after walking long distances, I wonder if that is a cause. I'll share, too, that I think I have some swelling that occurs with overuse. It is very subtle, but I will sometimes feel like nerves are being pinched when I do something new or strenuous. My cure? ice, elevation, backing off, and swimming. Being in the water seems to restore the what would you call it, proper pressure to my legs.