Vagina's Scent (tmi)

why do my lips smell like sweat or something like that? when i go shower i'm good and smell normal, but after about two or three hours i start smelling like that again. it's not strong, because i can only smell it if i rub my lips and bring my fingers up to my nose, but why? is it normal or? like it's only my lips, and it's not like i've been sweating either .. so?