Low breast milk supply

Hi everyone! My baby is 11 weeks, this is my first child. My breast milk is still not flowing as much as I’d like. I’m pumping a total of about 20-30 ml. a session. And that’s a good pumping session for me. My left boob usually more than my right. I’ve tried power pumping, lactation drinks and cookies. I drink plenty of water throughout the day. And baby latches on well when breastfeeding. I’m having to supplement with formula a lot more than I’d like to. Any advice?