HELP! DIAPER RASH!

My son is one week old and has had this awful rash on his bum really red raw looking I’ve tried Boudreaux‘s Butt paste and the extra strength Desitin for him nothing seems to be helping not sure what else to use or what other remedies I should try! I have a call into the doctors office but it looks painful I feel awful! My other two kiddos always use Boudreaux‘s Butt paste and the extra strength Desitin so I’m at a loss for what to try next. Literally feel like the worst mom ever right now.