Increase breastmilk supply at 19 days.

Hello, I gave birth to twins on 14th March via c section. My milk supply increased by constant pumping till 6th day and my breasts were very engorged day and night on 6,7,8th day after birth but I was in too much pain and tired and I did not pump and eat much during that time. Then breastmilk supply reduced. I also latched babies from 11th day and they nursed for half hour at one strech but I was not sure how much milk they are getting. We kept formula feeding them as well. Now I am again pumping and see very less supply. It's 30ml only at one time. Can I increase my breastmilk supply at 19 days postpartum or is it too late? I am a first time mom and I didn't know there is a fixed timeline till when you can increase your milk supply and I am very worried now.