The amount of breastmilk produced increases at about 3 or 4 days after birth, and the "mature" milk is said to have "come in."
Your baby will still nurse at least 8 to 12 times every day with varying lengths of time at the breast, from about 10-30 minutes. It's not essential to time your feedings you can let your baby nurse freely especially if they have a proper latch.
You may notice that your breasts feel full, heavy, or warm when your milk comes in.
Some mothers have painful engorgement due to increased milk volume and tissue swelling. The breasts feel hard and tight. The areola and nipple may seem stretched and flat, making it difficult for a baby to latch-on. The most important thing to do when your milk first comes in is to move the milk out of your breasts by feeding your baby frequently. If your baby has difficulty latching on because of severe engorgement resulting in flat nipples:
Stools should be changing from dark, tarry meconium to a brown or green color.
Bowel movements become looser. When your milk is in and baby is feeding well, stool will be a mustard-yellow, loose and seedy. By day 6 your baby should have at least 6 wet diapers every day and 4 poopy diapers.