Feeding mothers on exclusive breastfeeding, can you advise me? My brea…

Feeding mothers on exclusive breastfeeding, can you advise me? My breast has different sizes, the left one is larger and fills with milk more often and it hurts mainly, and I feed from it. The right one is smaller and soft like a rag always and leaks from it, but there's milk, but I don't feel like it's filling up, the baby doesn't suck it much.