Severe cramping?

I'm 23 weeks and went into Emerg today with terrible cramping on my left bottom side of my stomache, it was enough for me to be in the fetal position in a ridiculous amount of pain. Has anyone experienced this? The doctors did all sorts of tests and couldn't tell me anything other then it might be from constipation; except I haven't had any constipation and have daily bowel movements. Can anyone relate?