Help! Iam doing formula n breast milk both. 70/30. Who eles doing both

Tota • Vet 🥼 ! LA girl ! 👧🏻 1st time pregnant 🤰! EDD June ! Dog Mommy 🐶🐶 🐶

I need help to switch to breast milk only . Am pumping. My son dosnt latch . He is a premie. Hence I pump only 3 oz in one day and the rest is formula . Anybody out there doing both . How much formula and how much breast milk ? Are you happy doing both or do anyone wants to switch to breast milk only .