DS is ebf but am trying to give him a bottle of expressed milk every couple of days to make sure he remembers how to take a bottle. I am lucky in that I can express about 150ml (from one side) in 5/10mins (and then can't express any more). This doesn't seem to satisfy him, even though he only ever takes one side per feed. Does 150ml sound like enough or should I be adding in a bit of formula? He's a big baby...5weeks and 13lb.