Has anyone else had this, and it dosen't seem related to a cramp?

I've had this very painful butt muscle for about a week, and its agony, I have trouble putting pants on becuase it hurts and it randomly spasams when I'm sitting causing me to cry out in pain.

What the??

I haven't done anything strenuous I can think of to pull a muscle or anything do you think I had a cramp and didn't notice and now its just not getting better?

Thanks