Out of curiosity, with everything you have been through, everything you continue to go through,...do you have any impairment in the nerves in your lumbar spine?
(I know, not like another thing to think about, right?)
I only ask because that is what happened to me. Not necessarily pain, but my legs would give out. First it was one, then it was the other, and just like you, I cannot walk in big stores like Walmart or Home Depot. (The grocery store is enough of a challenge, even with the benefit of holding onto a cart, which helps).
But my legs, without notice, would give out, and I'd collapse. They'd just buckle.
I'm not sure if you've explained it before, but do you know why this is happening to you?
I wish you could get a break with everything going on!
M.