This is normal for some mummies, you can try to direct latch on the first breast before the other. Continue pumping each breast for 15 to 20 mins. As this is just 12 days postpartum, it will definitely take time. You can also request for breast massage from massuese and they be able to advice. My milk flow wasn't stable for one of my breast, after massage, maintain food intake then I'm able to get more supply. But then again, result depend on individual. Don't give up.