We are having similar issues here - not every night but most. DS is about 27 months old and has been in a toddler bed for about 6 weeks. Prior to that I was doing a lot of sitting with him while he fell asleep - in the evening then at every wake up OFten for hours at a time. He wanted me right there in his doorway. It totally sucked on the rough nights and I'm not pg so you have my sympathy hun!

Things we do here:
*We talk at other times during the day about bed & sleeping (book characters, TV shows, toys etc) and about sleeping at night (all night) and not getting up until the sun comes up. We have a rule where he can only get into our bed for cuddles once the sun is up so when he wanders in before dawn we take him back to bed. Sometimes he has a bit of a cuddle and then he gets back into bed and we say good night and leave.
* He goes to sleep with a couple of soft toys. Lately the number has grown a bit but DP has been away so I figured it was about DS needing more security. He calls them his 'friends'. Sometimes in the middle of the night he will say he needs more 'friends' and so I get him another 2-3 small soft toys. I try to give him different ones/rotate them so they are a bit new and he doesn't do this every night. This means he is happy to remain in bed alone until he drops back off to sleep. I have heard other parents leave books and toys etc (depending on lighting) for their kids at the end of the bed.
* I have started limiting his day sleeps and have the daycare centre waking him after 1 hour when he is there. I don't let him sleep longer than an hour here and if we get to say 2pm without a daysleep then he doesn't have one that day. He was catching up during the day (I think) and this meant he was not as tired overnight and was able to stay awake longer. If he is not keen to go to sleep during the day I don't push it (never really did but he is now having more sleep-free days as he gets older). This tactic is probably the most helpful in that we have had a few great nights since we started it last week. The shockers we've had lately are teeth related I think.

I HTH. For what it's worth I have been to sleep school with DS when he was 17m old and it didn't really work. At your DD's age, the staff will work more on your consistency with her I think and getting her to stay in her bed. So if you guys can pick a strategy or two and stay consistent I'm not sure you'll gain much more from going to school. WRT the staying in bed strict obedience thing, I'm not comfy with that for DS. I want him to feel he is safe to come and wake us if he has a problem in the middle of the night y'know? From what I witnessed with the older toddlers at sleep school, they will be very hardline with your DD following the rules etc. You can always call the parenting lines those places have and get some advice/tips etc over the phone too. (Not trying to turn you off sleep school, you know what you need, just sharing my opinion/experience).

I wonder if your DD is aware of your pg and feeling a bit more insecure lately because she understands on some level that things will change in the family? Or maybe you are at the horrible stage (as are we) of being between needing a decent day sleep and not needing it so much?

hun. This too shall pass. Hopefully soon.

Oh one last thing. I find when I expect DS to sleep though/sleep better etc I am much more agitated and upset when he doesn't. I have had many episodes of 'losing it' like you described Lately I have been trying to re-frame the situation as this is just part of who he is. We've had pretty consistent sleep issues of one type or another his whole life and I am starting to believe that he will just be a kid/teen/adult who doesn't sleep well. Plenty of my friends and even DP aren't the greatest sleepers. So I have started to expect that he will continue to wake me on a regular/semi-regular basis. That has helped my POV and ability to remain calm/patient enormously. I'm sorry that's probably not the type of strategy you were hoping to hear but it has helped me to do this.