Girls, I think I'm producing too little milk because I feel like the b…

Girls, I think I'm producing too little milk because I feel like the baby isn't getting enough and starts crying, I have to supplement with formula, which makes colic worse. Who has experienced such a situation? How can I increase my milk supply? I'm trying to breastfeed more often, but it's useless. I also heard that there should be enough milk for all three children by nature, but this seems not to be the case for me ? I started taking Apisal, as recommended by the pediatrician, a bit more came out, but they still aren't getting full ?