I thought 50ml was enough for a newborn? They only have small tummies don't they?

I think there's a sticky about increasing supply somewhere, perhaps in the general bfing section. Frequent feeds is a great thing though, as bub sucking will stimulate your supply.

Perhaps google for the growth charts based solely on breastfed babies, I think the charts in our blue books are based on formula fed babies? Both mine were 'underweight' as babies, but Riv's fine now, and Si looks fine to me too. Charting your bub's growth on the breastfed charts (I think I found mine from the ABA website?) might give you some peace of mind too.

ETA: Oh, and as for one more than the other - common! So don't worry about that!