i think it depends alot on where you are carrying and the uterus.
i dont honestly know when i "poped" because i think my body 'realxed' fairly fast and i've always had a pot belly so its depenant on alot of things too i guess...
i hope you pop soon...but be warned its hard to...erm...navagate around things when it happens (a slicer at work kept bumping my belly cus i didnt step back far enough! hah!)