Hi Avi,
I also breastfed exclusively and like Erin's girl, my son would have a big (yes, 'explosive' really describes it) bowel movement every few days. It was always soft too. Our trouble started when we began solids. We started with rice cereals when he was 5+ mths old and then for the next 2 months, the poor guy could only go once in 2 weeks. Mind you, it wasn't hard or dry, but he cut down quite a bit on nursing and didn't put on any weight during that time! Our doctor said it was OK as his tummy wasn't bloated. Apparently our son's gut needed time to adjust to working on solids, since breastmilk was so easy to digest before. Our doctor also said that rice cereals can have a constipating effect on some bablies. So I started giving him fruit too and everything turned out fine.