Not shure about this but I think I have some vague recollections about a fic that might fit this description.
Did Kagome have flashbacks where she relived the female youkai's life? I particularly remember a scene where the young lovers were caught making out by sess's father. (With her hanging upside-down in av tree?)
Was Kagome trapped several years underground? (I think this happened after they mated).
As I recall this story was long, complex and incomplete, I believe the name was 'The Luna Stone' and it was taken down from fanfiction.net several years ago.
(Don't remember the author's name unfortunately).