What is on my son? ADVICE PLEASE

Has anyone seen anything like this? I just took him to the dr yesterday for bug bites (in different areas, he’s very sensitive to bug bites) but now this weird rash is forming. He usually gets something like this every summer on his feet but now it’s on his tummy and ankles and it itches him. I’m taking him to the dr again in the morning. Just wonder if anyone has seen anything like this.