My lo is 4 months old and sleeps from 8 pm to 5 am. In between I feed him ebm twice. Is this sufficient?

Studies have shown that breastfed babies between 1 to 6 months take in an average of 25 oz or 750 ml per day. As long as your baby gets that amount of milk thereabouts, daily - inclusive of those two night feeds - it should be okay :)