I thought the courts took the view that a child of 12 or above can choose where to go (mum or dad), but a child under that age is deemd to be still a child, and residency is awarded on that basis. Therefore at the moment your dd should be where she was originally.
I feel very sorry for her, her dad's partner has left with 2 potential stepsisiters, and you are pregnant. Where is she in all this?
FWIW, I have sc who live with us all the time, they are teenagers and it is hard, very hard work at times. However, they are my DP's children, and they came as a package with him. I could never, and would never say they can't live with us, it would break dp's heart, and it is just a scenario I cannot imagine having any part in. I have to put up with awful noise all the time, guitars, music tv all full blast, it drives me mad, but I just have to get on with it.
I think you need to ask dp why he feels like this, and also possibly how has he reached age of 46 with no dc's? Does he not like them?
I was seeing a guy when my ds was young, who told him to go and lie face down in a lake. My ds was 2 at the time, I hate that guy with a vengenance 11 years later, and broke it off straight away. If your dp loves you, he should accept your daughter fully as well.
I would talk to him about it all, but if you refuse to let your daughter come and live with you, then you have probably lost her. At 11 years old all girls are interested in babies, she might end up being a big help, if only your dp realises.