Diaper rash or yeast infection?

My LO has had a red bum for about 5 days now. We have been airing her out, bathing her, giving her naked time, and putting diaper cream (aquaphor) on her every day. But her redness doesn’t seem to be getting better. It’s not like bright red and it’s not like in the crease of her butt (sorry tmi) it’s like on her cheeks and it’s just 2 lines. I’m gonna call the doctor but since tomorrow is a holiday I thought I’d check on here. I do have nystatin so I could use that if it’s a yeast infection. Thanks in advance!