I know there are other threads on this so sorry to go over old ground, but I am very confused. DS is 4 weeks old today. Because we were forced to use formula milk in the first week (before my milk came in) we have continued to give him just one formula feed on a Friday night and one on a Saturday night, to give me a break. DS doesn't seem to mind, but admittedly my breasts are pretty heavy, leaky and uncomfortable by the next feed at 3-4am. Am I doing any harm to my milk supply or to DS's ability to breastfeed? Should I breastfeed exclusively for a few weeks? What would be the benefit of expressing instead of formula feeding? If expressing is better, when should I do it? Apart from the nights when we formula feed, my milk supply seems exactly right, so I don't understand when best to express. Any advice please?