Diaper rash or yeast infection?

He's had this rash for over a week now! Since the very beginning we've been using diaper cream (tried several), changing his diapers frequently, using cotton wipes with water only, airing out his booty & drying it with a cool blow dryer. We just got a prescription diaper cream yesterday, and it's still just getting worse. Do y'all think it may be yeast?!?