Why milk is going behind the let down massage cushion?

Try leaning slightly forward when pumping. If milk still continues to draw up the back of the cushion, remove and re fit the let down massage cushion to ensure it is firmly attached and pushed far enough down the centre of the funnel. Some may prefer to use the pump without the let down massage cushion. The let down massage cushion has petals that flex in and out to gently massage the area around the breast. This is intended to stimulate a fast, natural milk flow.