How do you not worry?

Im a new mom. My baby girl is 8 weeks old. I’ve been a nanny for the past 5 years and have been babysitting before that for 7 years. I’ve always been around kids of all ages. I was very calm and collected and would know exactly what to do with every situation. But now with my own child, I feel like everything is a mistake and I worry about everything. She was in her car seat for over 2 hours the other day while I had errands to run (something I know now is too long to have your child in there for.... no one had ever told me there was a time limit), and she got an irritation from the newborn pad and the outfit she was wearing. It had turned into a scab and I was keeping it covered the best I could (it’s the back of her shoulder near her armpit so she is always moving), this morning I was changing the pad because it came off so much, and the whole thing is red and more irritated and larger. I called her pediatrician right away and they can’t get her in until this afternoon. I feel so terrible! I don’t know what I did! I don’t want to put her down because I don’t want anything rubbing on it making it worse! I don’t know if it’s infected or if its just the area it’s at and constant moving or if it is something worse and more serious. I’m so scared and I feel like I messed up and it terrifies me putting her back in her car seat to take her to the doctors because it’ll only irritate it more. I just want to get it looked at but sitting around all day waiting is making me a nervous wreck and I can’t stop crying. How do you not worry about every little thing?! How do you know what to do?

First I was keeping it open and letting it air dry but then everything I read said babies need to have cuts and things covered and shouldn’t be exposed to air. So I started keeping it covered and now it’s so much worse. I’m just so scared and I wish I could’ve just taken her to the doctors right away and not wait around all day. Plus she hasn’t been acting any different at all, she doesn’t have a fever, whenever I’m looking at it r covering it she doesn’t act like it’s bothering her.

I’m already a nervous person, but now having a baby, everything worries me so much more and now this, I just feel so paranoid at every little thing because of something I thought was so minuscule.