What Causes Rashes Along With Severe Itching Under The Breasts?

About 3 weeks ago, I had pain in torso area, under bra area and around back. I saw my doctor who suspected I had shingles. I took a blood test but he put me on antiviral meds right away. Blood test came back positive for the virus and pain went away after taking medication. No rash developed but now I believe I am getting a rash in the same area. The itching is bad and area red on and off. I thought you could not get shingles a second time. Is it possible that anti viral did not work? By the way I am 55 and female.