help! diaper rash!

Can anyone suggest any remedies for my poor child! He is 16 weeks and gets really bad diaper rash! He is not crying but this must hurt! Also before you judge he showers every single night and gets his butt washed instead of cleaned with wipes every time we have been to the doc many times and no creams - remedies are working! I also changed his diapers and I see no result! Help!!!!