Breast feeding

When my little boy came I exclusively wanted to bf. When I had him I started breast feeding but he seemed to wake every hour for more and I was not sure if it was enough. He had to go to nicu for further testing for his kidney, they were feeding him formula. He has been eating 2oz on top of breast feeding. He seems to not be getting enough from me and it makes me sad. He is now almost 3 days old. What can I do to increase supply. I am still in hospital and will be getting discharged later today.