breastmilk works in supply and demand. you got to nurse more during the initial stage before it established. if you want more milk you got to pump after nursing to stimulate. but do take note pumping is very tiring. alternative you can nurse one side and haakaa the other side
This may helps you - https://sg.theasianparent.com/how-to-increase-breast-milk-supply
Don’t miss a pump even if it’s every 3 hours.