Hi Chick
I am gate crashing from DIJanuary, but thought I'd share my tmi brown experience with you.
I had something that sounded like this at 17 weeks, they couldnt find an infection but as my cervix was shortening they put me on antibiotics and that fixed it, within a day it had stopped and my cervix had lengthend by a whole 10mm, so scared and worried at the time though, as I had some cervix removed a few years before for a cancer scare I was sent to the gynea clinic they classed it as threatend miscarriage, but by then it was all fine and baby is due in 10 days x
You should get it checked if its still happening as it may mean infection which obviously you would need clearing up. Hope its cleared up by itself x