|most likely you got it when you took your clothes off or went to the bathroom. If there was oil on your hands and you touched another area of exposed skin, it will spread.
I got a terrible case on my arms. I know i got my arms exposed, but not my body. But, when i went to take a shower, my arms touched my sides and legs. I obviously didnt wash off my body good enough to remove the oil. Since the oil wasn't as strong, it broke out a few days later and wasnt as bad as my arms.