You know I know....but I have no advice.
I've had 3 terrible sleepers. Only now, at 4yrs old is DD sleeping through the night more often than not. DS2 is waking 1-2hrly at night and is up for the day by 6am. I must say though he sleeps ok though the day.
Have you had her chacked out by a paed? I have no idea what could be wrong with her, but maybe there's something medical? I know she has issues with food sensitivities...maybe it's still that? Maybe her ears or something?? I don't know hunny.
I'm so sorry that you have to go through this, it really is torturous, especially when pg. DD was my worst sleeper, and when I was pg, it was so hard. Plus I was working, and crazily enough studying part time too. It was a VERY long few months until I stopped working and finished studying.
All I can tell you is rest when you can. Take advantage of offers of help from everyone and anyone, and if someone takes bub out, SLEEP! Don't clean or cook or anything like that, rest.