I feel like such a bad mom

My little one has a really bad diaper rash. First it was on her butt, I bought desitin and it seemed to work but her butt area still looks red and irritated. Now there’s red bump on her vulva and to the side. She also has a white tongue and I don’t know if it’s from the milk or if it’s thrush. I tried cleaning her tongue but she doesn’t open wide enough for me and honestly I feel so defeated. I’m giving her pediatrician a call tomorrow and I hope they let me come in this week.