If your baby is having breastmilk only (no formula, solids or water) and is having six to eight really wet cloth nappies or five heavily wet disposables in 24 hours, and soft bowel motions; then you know plenty of milk is going in the other end.
It can be that you are expecting your baby to ask for feeds every four hours. This is an unlikely frequency for newborns and many older babies. Most newborns want to breastfeed between eight and twelve times in 24 hours; many will feed even more often.
Breastmilk is food and drink and comfort to babies. Your baby doesn't know that she's hungry or thirsty, she just knows she needs you. As adults we help ourselves to a drink or snack many times a day, and can quite happily manage a cup of coffee or tea straight after we've eaten. Your little baby has a tiny stomach which needs refilling very often. If she's hungry, give her more breastfeeds and see our article on increasing your milk supply.