Diaper rash question

My daughter has a flat, red, quarter sized rash. It doesn't look like typical diaper rash, it is not on her bottom, it is on top where the front of her diaper is. It keeps coming and going for a few weeks now. Tonight it looks redder and almost like a burn. I have a call in to our after hours pediatrician but they won't advise much other than what we have been doing. Anyone ever have anything similar?