Why, when I've been stood up for a while and then sit down, do I get a lot of shooting pains in my back and sides?

[NatalieJaneIsPregnantAgain]

I don't mean like a sharp pain, but a sharp ache, it throbs with my pulse and almost stops me breathing properly. I can't stop myself from physically moving (almost like a whole upper boddy twitch) with the throbs. Lasts for 10 seconds or so, then goes and no pain whatsoever is left. Is it just him sat on nerves etc? Can't remember it happening with my first two.

I am 36 weeks tomorrow.

Tut, body, not boddy!

I don't know what it is but it sounds a bit horrid. Maybe ring your midwife? xx