What causes large stool (length and width)?

This is a gross question ... I know. But it's life and we all do it. I have always had extra-large stool. What could be the cause of this? It is sometimes very hard to go the bathroom due to the pain. I also get constipated sometimes. I would say the length is anywhere from 6-7 inches and 2-3 inches.
Update: Correction - 6 to 7 inches in length and 2 to 3 inches in width.
14 answers 14