Rash that won't heal

About a year ago I got this rash on my belly just below and the right of my belly button about the size of a quarter - over time is spread so I went to a doctor about three months ago when I developed a rash on my armpits.  The doctor told me it looked like a fungal rash on my armpits and an allergy from my belt on my belly.  A fungal cream and changing my antiperspirant cleared up the armpit rash but a prescribed cortisone cream did nothing for my belly.

I haven't worn a belt since that day and am careful to tuck in my shirts but my rash will dry up, flake and peel, then the skin will turn bright purplish red, raise, itch, burn and start again.  In the past few weeks it has started to spread and is now about the size of a grapefruit.