I'm going to offer some different ideas although I think the other posters have some great suggestions. Does she watch any TV yet? Is she into any of those kids shows on ABC kids? Many of them have CD's or on itunes you can download story tracks only (no video) so you could get her to lie down and "listen to the story." What about one of those baby lights that shines lights and plays music at the same time? Perhaps your DD is now associating bedtime with negativity and making it a bit more fun but still calming/relaxing might break that cycle. Can you give her a little torch of her own to play with when it's bed time? Does she have a dolly? Can you try and get to her to lie quietly with her dolly stroking it's back while you sit in the room and sing to her quietly or tell her a story in the dim light?

We pat my DD when she goes to bed. It's less than ideal and sometimes we are in there for 20 minutes or so. She was one of those kids where I could put her in and shut the door and just changed in the last 6 months or so. I think kids go through phases. It's hard, especially when you are pregnant. I really feel for you and I hope that one of these ideas works for you guys.