This has happened to me once or twice before, but not in the same way. I am expecting my period and this morning i woke up with what i assume is gas. I feel constipated (but had a bowel movement in spurts this morning), the pain is right at the bottom of my back at the top of my butt. I can sit down but moving from a seated position to a different one brings pain. dull hard pain, not sharp, not spasming. I can walk easily once I am standing, but getting up from a seated position is scarey, and when seated, shifting brings pain also. Should I be worried, might this be something other than menstrual cycle related? How do I get relief?