Scott, thank you for posting this. You were able to articulate my symptoms almost exactly to a Tee as what I am experiencing. (only I get HOT hot HOT rather than shivers) Other than that, I am dealing with the same. I now have some answers that I can go with, I would like to be able to walk for more than 5 minutes
Good luck to you, Scott!
...and thank you to all those who replied to this thread as I am lurking about and using the information for me!!!