sore places on feet

I get strange places on my feet that are very painful. They seem to occur anywhere on my foot randomly. It will start out as an itchy, burning spot, then the tissue underneath the skin will harden and become extremely tender. The place (and sometimes my whole foot) will swell until sometimes I cannot even walk. This usually lasts about 24 hours. I have asked doctors about it, who always tell me to apply hydrocortisone cream. I cannot get anyone to understand that the itching is coming from underneath the skin. Please help.