I had some pretty major pain at 9dpo. I had been moving alot of very heavy boxes and honestly thought I might be getting a hernia. My pain was perfectly centered, right where my uterus is. It lasted about half a day, the next day it was still there, but fading.
I am now 15dpo and had a few lighter versions of the same thing yesterday. Only, it didn't hurt like before, it feels more like pulling.
Oh, I'm pregnant, so I'm pretty sure mine were caused by implantation.