Are you referring to like sharp pains and spasms in the bum area? If yes, then I have that too! I am now 10 weeks pregnant and I have been experiencing that since like 2 weeks ago.
I goggled on that and get stuff like a 'tilted uterus', "stretched ligament", etc. But the main idea that I got was that this was basically common among pregnant mothers. I'm just curious too 'cause none of my preggie friends ever had that experience.