In need of advice!

hey guys, my daughter is 3 weeks old. I didn't start pumping breast milk until she was 5 days old, before that I was giving her formula because she wouldn't latch on at all! When I first started pumping I pumped every 2-3 hours and got a little over 6oz every time. Just a few days ago I stopped pumping as often... I went from pumping every 2-3 hours to pumping when ever I got a chance which was 5 hours and sometimes more. in between pumping she started to breast feed for at least 20 minutes every time. Now when I try to pump every 3 hours I get 3oz or less. What can I do to pump more? Do lactation teas, cookies and vitamins actually work? I tired power pumping, but I only got a couple drops.