Suggest Treatment For Red Rashes All Over

i had a alergic reaction to medicine when i was sick and they gave me medicine for the reaction it was red rash it didnt itch or anything , but recently like 3 months after i took the steroids for the rash it turned brown and now its like all over my back but not in the middle by my spine and it spread to under my chest . im 15 year old girl and kind of freaked out .