Make sure that your nipple is not touching the silicone at all, because if it does, it may hurt. This is especially true if you are pumping to rest your nipples that are sore from nursing. Avoid putting them under any unnecessary pressure. Haakaa's way of pumping milk is different from regular manual or electric pumps which press and release repeatedly. With the Haakaa, the suction is continuous so you need to check it is attached comfortably and adjust it if not.