Really bad nappy rash

My LO is 3 weeks old and has horrible nappy rash. I'm on antibiotics so I think that might be the reason why because she is breastfed. I'm taking probiotics and she has special baby probiotics, we have all these creams, powders and ointments that seem like they're doing nothing. She screams so much when we try to do nappy free time to air it out and it just breaks my heart 😢 we can't get into the doctors until Tuesday but hopefully they will give us a steroid cream but I'm honestly at my wit's end.