If your breasts are uncomfortably full and engorged it is important that you express some milk until they are soft and comfortable again. Otherwise you put yourself at risk of mastitis. Right now your milk supply is driven by the high levels of hormones in your body. You are just churning out milk, and you have to keep moving it. It's not until a bit further down the track that breastfeeding works more on supply and demand So, express some milk (or pick up the baby and feed her again) and put on an icepack to relieve it a bit.