Crazy rash taking over my son's body!!

We've been battling this rash for 2 months! We've seen 4 different pediatricians and only one of them actually prescribed something to help it (a steroid ointment) which it worked the first time I used it on him, but the second time it was like it burnt him!! As soon as I put it on he started screaming and everywhere I had put it was bright red and pussy! I called them and told them about it, their response was to keep using it!! So I give up on the pediatricians, I called a dermatologist 2 weeks ago and they couldn't get him in until the 9th. I have never seen a rash like this before and it just keeps spreading!! It started put looking like cradle cap on his head and then it turned green and pussy, then it started on his right cheek, then his elbows, his thumbs, his left cheek, his eyebrows, now his back and it's starting on his chest now too! Obviously we're seeing as many doctors we can, but has anyone seen something like this before?