Hi haloflo
I could have written your original post myself :)
I too had the same shooting pain in my bum cheek which was debilitating. Would be wincing down the corridor at work with every step....
I went to the GP on the Thursday and was referred to the physio and seen the following Wednesday.
The physio informed me that this kind of pain is not uncommon in pregnancy, she had a look to make sure that everything was roughly aligned (i.e. no bulging discs or anything?), and said I could take paracetemol and try do gentle stretches. She said that if it got worse, I could self refer back and there are belt supports, crutches etc that could help.
A week has passed since the physio, and the pain has definitely eased a bit. Oddly enough, it seems to be only slightly discomforting, but in both bum cheeks now!! While I am still aware of it, I am certainly not wincing in pain as much at all anymore.
When I was researching all this online before going to the GP, I also found out about Piriformis Syndrome which is very common in pregnancy, and is exactly like the pains I think we are experiencing. It is closely related to sciatica - but different. With sciatica, you get shooting pains down your legs, which I certainly wasn't getting. It was more like the pain was in my bones/bum cheeks. So, it could be that?
Irrespective, I think that the solution is the same (assuming its not a something more serious). Take regular breaks from your desk, stretch as much as you can, take paracetemol if needed, and keep an eye on it in case you need a belt support or something.
Hope the pain eases soon...