Your breasts are probably engorged. Engorgement happens in the first two to five days after delivery when your milk first comes in.
Why it happens: "When the milk ducts fill with milk, the body launches an inflammatory response. Blood flow increases to the breasts, and they can become swollen, hard, tender, and even warm or reddened," says Summer Cassidy, R.N., a certified lactation consultant in the NICU at Advocate Lutheran General Children's Hospital in Park Ridge, Illinois. Engorgement can also happen later, though, if you've skipped a nursing session or if your breasts aren't fully drained during pumping or nursing sessions.
What to do: Nurse or pump often. After your milk first comes in, make sure to pump or feed every two to three hours during the day and every three hours at night. A warm compress before feeding or pumping can facilitate the milk flow, otherwise use cold packs between feedings to ease the discomfort. Talk to your doctor about taking ibuprofen for pain, too. Also, try this trick: Hand-express some milk in the shower before your next feeding. "A hot shower is a good way to soften the swollen areolar area, which can compress ducts and impede milk flow," says Cassidy. "Express as much milk as you can in the shower and then pump or breastfeed immediately afterward."