Well, this might not be very scientific but I think Baby Boo moved somehow while I was swimming yesterday. In the new position she was squashing my bladder and I felt like I was BUSTING to pee... but it was only a few drops each time.
After several (like about six in three hours) trips to the loo, I decided to try the bum in the air head down thing that was recommended to you.
So I was doing that on the couch when DP walked past and thought it would be really funny to give me a Hopoate-style poke. So I jumped in the air and starting thinking murderous thoughts about the now not-so-D P.
But after a few hours I realised the urge to pee had vanished. So somehow that combination of things seemed to have moved her. I'm not sure I would recommend this system. This is more of an observation, really.
Good luck, though, Rach. What you're going through really doesn't sound pleasant.