Oh Chachi good luck to you!
Are you walking a marathon literally? I used to do the Walk for Hunger in Boston, MA every year for about 8 years in a row. It's a 20 mile walk. It was HARD to walk that much. I usually did really good until like mile 16, then I crapped out and still had 4 miles to go!!! Oh it was painful.... and I did it when I was in good shape, but not prepared for a 20 mile walk... I was a lot younger then too!