foot pressure pain??

I am 37, my feet hurt only when i stand, or walk a lot. I have been to 3 docs, had xrays, every type of insert, including 2 custom. Nothing works, I can ride my bike with ease, and even run on the treadmill a mile or so. Pain usually when the day ends, but not always. Im 5 10, weigh 185. If I sit or elevate my feet, no pain at all. Only when pressure is applied. Could it be something to do with iron, thyroid, vitamin deficiency??? Something other than the traditionals: planter, nerve, arch issues? I have a high tolerance for pain and can function pretty normal, it just gets to me sometimes, and i worry about the future. Any helpful ideas???? thanks!