I was reading it on ff.net it wasn't completed and was being updated so its a current working story.

it starts with Kagome waking in a bed next to a guy bankotus she went out with friends and someone spiked her drink thus letting bankotus rape her. her grandmother works for Sesshomaru helping with his two daughters, he would take his youngest to work with him. i remember that at one point kagome took her grandmothers place for a time and then started seeing sesshomaru and having all kinds of strange things happen.

I can't remember if they had slept together before i stopped reading of not but i remember that kagome being pregnant was hinted at.

I think that it is call "Her Happiness" by Rockhard Angel. It is rated "M" www.fanfiction.net/s/6995974/1/Her-Happiness

YES! omg thank you so much this was bugging me for a month.