I have no idea how long it should hang around for, sorry.

From my experience it's all part of being pregnant... I would go from being severly constipated (on meds ect) to having diahorrea in a matter of days. I was a yo-yo for at least the first 20 or so weeks before it settled down a little bit. Even without taking anything for the constipation it would still happen!

I think if you are concerned then ring your hospital, dr or even the chemist for some advice.