I went through the exact same thing when I was pg! Then when she was born, suddenly I had heaps and heaps of new friends, from Mother's group, and just random people I'd known from years before that have had kids too and now we have something in common and become good friends (even when we weren't relaly friends at all before, eg people from highschool)
I have far more friends now than ever before, and my old friends from before DD are just old acquaintances now.
TBH, having DD is the best thing to ever happen to my social life.