What Causes Excruciating Pain On The Top Of The Butt Crack?

Hi, I'm a 32 yr old female- I have excruciating pain about 2 inches down from the top of my buttcrack. No visible injury, havent fallen- Very tender to the touch, very painful with movement (getting up, turning over) and seems to be worse with movement of my left leg (rotating hip or putting weight on left foot when walking) Any idea what this could be? Ive been miserable for 3 days!