Hard poo (constipation) is very rare among EBF babies.. I do hope you are not confusing the groaning as constipation? Most babies groan even with pasty stool. And it's OK if an EBF doesn't poo everyday or even up to 2 weeks but if truly the poo of your EBF is hard as in like an adult poo, then there's need to investigate by a paediatrician or paediatric surgeon