What Causes Discoloration Of Penile Foreskin?

I have White discolouration to foreskin approximate two years, some tightness retracting foreskin, more recently spreading, now around whole of tip of foreskin about one cm deep, treated with topical steroid cream which reduces tightness but no effect on rash, sometimes becomes inflamed, do you know what this is?? I suspect box, doctor says continue with creams??