Boobs are hard today and yesterday they were soft

Day 9 of breastfeeding Boobs are hard today and yesterday they were soft. What does it mean when they are hard? He's 9 days old and he's eating more day 7 that evening he cluster fed and during the day yesterday he did and today from about 8-2 he's been eating for 30 minutes every hour, my boobs also hurt more today than they have