so they want a kid and have trouble I think? But then one day they find a girl to take in. I think Connor and dawn are together. Then I'm sure buffy gets pregnant around the end of the first part of the series.

Maybe this one?...
The Baby Series by Mrs Muir

Summary: Series of four epic fics covering the Babyverse. Spike is called away by Drusilla before he can meet Buffy at the Bronze in Tabula Rasa. He doesn't return to Sunnydale until after the fiasco of Xander and Anya's wedding. Things aren't the same as when he left town...especially Buffy.