I've had walking problems for my entire life...
When I was very young, my right foot pointed inwards , and it flopped downwards when I walked. As I grew older, the flopping stopped, but my feet kept pointing inwards (my left had also pointed inwards, but much less so, and it never flopped).
From as far back as I can remember, I had a phenomenon where, out of the blue, my legs would get so tired they could barely carry me. I played soccer, and sometimes I would just, as the coach said, "lose my hustle". Start dragging around the field, walking after the pack chasing the ball, that sort of thing. This continued until I hit puberty.
When I hit puberty, I quit having my legs lose their strength, but I began to have severe pain in the arches of my feet. To this day, if I try to walk a distance of greater than 3/4ths of a mile, or stand for more than 2 hours, the pain starts, and gets more severe the longer I walk or longer I stand. I ended up quitting my last job because it involved standing behind a cash register, and it nearly crippled me.
Sadly, I've no advice... I've tried several different kinds of orthotics, including ones that cost multiple hundreds of dollars and were molded directly to my feet. The help has been inconsistent at best... when I hit puberty I nearly doubled in size, I currently weigh around 250, and my weight tends to crush the shape of my orthotics until they no longer serve the purpose. The only other option that I was given was plastic surgery, which barely counts. It isn't covered by insurance, would cost possibly over $10K, and wouldn't have anywhere near a certain success rate, and had a high rate for potentially crippling me.