I Have Flat Feet And My Feet Have Been In

I have flat feet and my feet have been in pain for over a year. ive seen a doctor and he just gave me cut outs of in soles. they didn't work. my feet are flat as pancakes. the area where the top of my foot where the leg and foot are together feels like a vein is boldging. I can feel the bubbliness of that vein. I work in retail 40 hrs a week and im on hard floor all day. what should I do and whats wrong with my feet?