Uneven milk production

My lo has started sleeping more at night but I woke up with full breasts so I pumped. I'm concerned I only got 1/2 oz from my left and 2 1/2 oz from my right. She is 3 weeks old and it was 4 hours since she last ate. This has been going on since day one. How can I get lefty to produce more. I use heat, drink the tea, let her feed on left first and in out of ideas.