Building milk supply

Alyssia • Thankful- Grateful- Blessed 🙌🏼🙏🏻 Alessandra Grace 💖 4/18/16 Leonel Jaxson 💙 1/22/20
FTM to beautiful 3 wk old. Since day 1 I have been BF on demand. I give her one side at a time unless she's super hungry than I do burp and alternate. I just read somewhere that in order to build milk supply in the first few early weeks you must give both sides at each feeding. Now I'm worried since I don't use both at each feeding am I still building up my supply for demand later? I have tried pumping in the last couple of days once daily and am able to produce just about 2-3 oz each side. Any moms can help me out with how to make sure I'm building my supply? Thanks in advance!