I am 18 years old i'm sexually active but my breast don't look fully developed. my breast look like there in the there in stage 5 will they grow?

Can't predict: Breast size, like penis size, depends upon individual. While there is some association w/age, there is no specific "normal" for any given age. Instead, we assess pubertal development by tanner stages. In theory, breast should be tanner stage v by 15yo which is described as "breast reaches final adult size; areola returns to contour of the surrounding breast, with a projecting central papilla".