Frequent feeding results in more milk
Breastfeeding works on the "supply-and-demand" principle—the more frequently you breastfeed or express, the more milk will be produced.
If you and your baby are separated, try to express breastmilk at least 8 times a day, including at least once during the night. Ask the hospital staff about storage of expressed milk.
All mothers worry whether their baby is getting "enough" breastmilk—this is completely normal. Ask your midwife or lactation consultant to observe and support you with a feed if you are unsure.