breastfeeding help

Hello everyone I'm a mom of 7 days now and have a question regarding breastfeeding. My baby eats like a champ and I seem to be getting lots of milk, but in the last 2 days I've noticed my left boob is always hard and hurts. I pumped out of my right boob and got 3 ounces but the left nothing comes out. When I put her on my left side she eats for like 20-30 minutes so I know the supply is there. HELP