Um..Help Finding a Fic?
The pairing is Xander/Spike. I know that for some reason Anya was hurt/dieing/or tired of being human and I'm pretty sure she got her powers back. She wanted Xander to have someone to love and/or take care of so she made Spike female and human too.
I remember one scene where Xander kinda gives Dawn ans femaleSpike the 'talk' and show them how to use condoms and have safe oral sex also..there were bannanas involved also ^_^ Eventualy Spike and Xander get together and Spike gets pregnant and gives birth. I know that after Spike gives birth he turns male and vapiric agian and is scared Xander does't want him anymore but they stay together.
EDIT: FOUND! by an Anonymous lurker. The fic is 'Love Me Like A Man' by Ruth Sadelle Alderson(http://www.graphousa.net/rsadelle/fiction/lmlaman.htm)