How To Get Rid Of Rashes All Over?

i have had a rash for 7 week and has not healed it is also spreading. I have seen so many doctors who have no idea what this is. curently the only 3 places it's not is my feet face and lower legs. The doctor just called and said blood tests came back normal your hemoglobin is just really low. why cant this rash just go away. please help