I have brown lines across my stomach to lines & i am not pregnant , ?

Is it ACROSS?: Obesity may cause skin discolorations across the body due to hormone changes called acanthosis nigricans, which are darkened, velvety areas of the neck and body folds. A vertical line typically runs from the pubic bone to the belly button, but can run all the way up to the chest in a pregnant woman. This linea nigra can be seen in nonpregnant women on the pill or with a hormonal disorder.