I went to dermatologist for red itchy rash on left groin and left arm. She prescribed a 12 day round of prednisone & prescription strength hydrocortisone cream. Also suggested I take Zyrtec at night to help sleep. Rash continues to spread yet not quite as itchy. This morning I noticed lines imanating out from several of the rash sites & my groin area is now purple. Should I go back to doctor