Rash has changed

Thursday came home from work felt flu like and loose BM and small fever. Woke up Friday fine. Saturday and Sunday felt kind tired. Sunday into Monday had a rash start. Went to doctor got a steroid shot. Woke up Thursday morning and the rash has changed into blisters. Went to doctor today. He had no idea what it was. I asked to be strep tested bc I am a teacher and we had some kids last week with it. It came back positive. The rash is painful,itch,swollen,blister.