Milk supply


My daughter is 5 weeks old. I had C Section, due to infection in the wound I couldn’t fully breast feed the baby and ended up giving her formula milk alongside. I have tried pumping to keep the flow but not much success. Yesterday I couldn’t breast feed her whole day but managed to pump 4 Ozs at night. Today she had my milk few times but every time I tried pumping nothing came out. My concern is the milk supply, how can I increase that? Is it too late or can milk supply improve? I haven’t been drinking much water lately though!!