Our little girl (born at 36 weeks) didn't come home with a rash but developed one almost as soon as we got home. It was VERY severe - red, raw and open sores. We tried absolutely everything to clear it. At first we thought it was from the cloth diapers, but switching to disposables didn't clear it. She is now 10 weeks and still has a rash but it is SO much improved. I won't list the million things we tried (including yeast cream) but what seems to have made the biggest difference is:
1. Pocket diapers (the ones with microfleece lining to wick away the moisture) paired with raw silk liners (these protect the diapers from the diaper cream and also seem to help clear her rash as it's worse with microfleece liners). Fuzzi Bunz seem to be the best, but other pocket diapers work well as well.
2. Triple Paste diaper rash cream (this is the best of the 8+ we tried).
3. As much open air on bum as possible - call this "bum time" in our house.
What is unfortunate is that we spent quite a bit of money on fitted diapers and diaper covers and now we really can't use them - the only time we can use them is if we're home we can put a fitted on without a cover and change it as soon as it's wet (often every 20 minutes). This keeps the rash to a minimum, but still not as good as when she's wearing pocket diapers.
Anyways, I know how awful it can be to worry about our little ones in pain with a bad rash. Good luck it.