Diaper Rash!?!?!?!

Any ideas on how to treat real, red, inflamed diaper rash? Evan is miserable. He has never even had a red behind until now. It started Tuesday when he must have woken up in the early morning for his morning poo, then fell back to sleep, because I found a mess when he woke me up in the morning at 7:30a. It seemed to have been there for awhile. He's never done this before. He has had problems with yeast down there, which yes, little boys still deal with as well because it also lives in poo. This started as a yeast infection and I think it is now just a plain old diaper rash. His problem with yeast always started in the places that no longer exist because of his circumcision, but now it started from this one time waking up in the morning, sitting who knows how long in his poo. I already feel like a bad mom for lots of things, then I go and let this happen. I'm not sure exactly how I could have prevented it, but that's good ol' "Mom guilt" for you.
Ideas would be great!!