Why is intercourse more painful after giving birth?

It could be possible that the wound has not entirely healed yet. If you've had a natural vaginal delivery, you most likely would have had stitches down there which takes a few weeks to heal, depending on the severity of the tear. Other reasons could be vaginal dryness due to breastfeeding. For that, you can use a lubricant. http://sg.theasianparent.com/sex_after_pregnancy/