I am exclusively breastfeeding my six month old. I thought that breastfed babies never got constipated. She is a Board Certified Lactation Consultant, as well as a retired La Leche League Leader. You are right, exclusively breastfed babies very rarely become constipated.
Constipation is defined as hard, dry, and difficult to pass stools.
In a breastfed baby older than about five to six weeks of age you may see a spacing of bowel movements. It is the hardness of the stools, and not the time between stools, that determines constipation in the breastfed baby. Exclusive breastfeeding actually means that a baby is offered nothing else by mouth except breastmilk. As solid foods are added to a baby's diet it is not unusual to see a change in the stooling pattern. You didn't necessarily give your little one too many solid foods.