This could be a simple case of jock itch, or some sort of fungal infection. However, getting tested and evaluated by a doctor or GP couldn't hurt...highly recommended.
herpes won't just cause itching. you were on antibiotics, it is probably just jock itch and you can treat that with otc products. if you think it's more than jock itch, be seen again for a work up.
grace
herpes can cause itching on the thighs legs buttock scrotum in what is known as the prodrome period which is right before you get an outbreak
also, if i may add herpes is often mistaken for jock itch razor burn ingrown hairs yeast infections etc