What is this?

Hello parents and/ or nurses I need some help. Any idea what this is on my baby's arm and back. I've asked her pediatrician twice. She said she doesn't want to say it's eczema but I have a strong feeling it is. I'm starting to get frustrated with her doctor and I'm thinking about getting a second opinion. I'm just curious of what you guys think. Parents have you experienced this with your babies? Thanks in advance.