What "size? flow?" nipple do you use on the bottles? I am still using the newborn ones because I fear LO getting a bottle preference if the milk flows faster than when I breastfeed him. My mom is complaining it takes way too long to feed him 5 oz out of the newborn nipple, but I am scared to move onto the 3 month one (he is 3 months today). If you breast and bottle feed, what nipple do you use and have you had any trouble with bottle preference or impatience on the breast? Thanks!