How to boost breastmilk supply?

My LO is 3 weeks old today, my breastmilk supply is low. I'm taking lactation treats, malunggay capsules, lactation drinks to boost it but still it is not enough. I usually get no more than 1oz per pump. I pump every 2-3hrs, my LO usually gets frustrated when he's trying to latch on me. He's currently on mix feeding since my milk supply is low.