After giving birth on January 18,2012 I had bleeding for about three and a half weeks but today when I woke up I'm bleeding again, not that heavy but a normal blood like menstruation,but I don't feel any discomfort.. What was this means?

After giving birth on January 18,2012 I had bleeding for about three and a half weeks but today when I woke up I'm bleeding again, not that heavy but a normal blood like menstruation,but I don't feel any discomfort.. I'm exclusively breastfeeding.. What was this means?