I have this too!!!

And I thought it was just bub bouncing on my pladder but I had it during my 20 week scan last week and she said it isnt bub but a Braxton Hicks (no idea how to spell it) contraction and that it's completely normal to start having them from about week 14 onwards.

Apparently it should only last for 15 minutes and it gives you that feeling like you need to pee but nothing much really happens if you try to go.

Kind of cool but also bizzare to think our body starts practicing so early!!

Tarsh