sharp pains in my booty.

Has anybody else experienced this... Sometimes, when I sit down, or have been sitting and lean forward to where most of my weight is on or around my anus (like the literal hole) I'll get a sharp twinge of pain. It goes away almost immediately, but was just wondering what it's from? I know at times, it is gas because I'll have to get up to go to the restroom so I can pee and pass the gas, but others there's no gas.