Your baby will go through several growth spurts at fairly predictable times. One typically sees this around 10-14 days of life, 6 weeks, 3 months and 6 months, but may be as frequent as every 2 weeks. Follow your baby's cues. He may be fussier and want to nurse more frequently. He will increase his breastfeeding for a day or two until the increased suckling produces an increased quantity of milk. Remember the more stimulation your breasts get, the more milk you will produce. Your baby will return to less frequent feedings after he has increased your milk supply.
Because the initial period of fullness in your breasts decreases at about the same time your baby experiences his 6 week growth spurt, some mothers fear they have "lost their milk". This is not the case. As long as you see signs that your baby is getting enough milk, you can be assured that your milk supply is meeting your baby's needs.