increase breastmilk

Im 2 wks pp. First week and a half, i latch on demand and gives formula. For the past few days, bby developed phlegm so i only latch and don't give formula. On top of direct latch, i pump 3 times a day at 12n, 4pm and 8pm. But my yield is only 15ml per breast. My diet wise since im on confinment, Breakfast is buisuits and milo, afternoon rice and milo, snack on fruits or bread and dinner only bread with milo. Ofc inbtwn i would drink mineral water , would finish atleast 3ltr of mineral water a day. But my breast milk is still very low. But bby sucks well when direct latch. Any one with experience to increase breastmilk?