What Causes A Rash On Inner Thigh And Base Of The Penis?

I have a red rash on my inner thigh and at the base of my penis that itches and has a shinyness to it. My posterior also itches at times. I went to the doctor and they said it is jock itch but i have tried Mentax for over a week along with earlier using lamisil and lotrimin. The rash doesn't seem to be going away could it be erythrasma instead of jock itch?