Kagome found Sesshoumaru from a parallel world and brought him to her world. This Sesshoumaru has a different(maybe opposite) personality from the Sesshoumaru we know. They both fall in love with Kagome. I think there was a moment where Sesshoumaru from her world felt jealous of her closeness with Sesshoumaru from the parallel world. Inuyasha was also sent to a parallel world (near the end or maybe in the middle of the story). Kikyo and Kagome from that world both become his girlfriends.

I'm sorry I can't remember more details. It's been 5 years, give or take, since I last read that fic. I also can't remember which website I read it from. It is a great story and I wish I could read it again.

Thank you! ^_^

I think you're looking for:
A Tangled Mess: The Mating Habits of Kagome Higurashi by Speedy Tomato.

It's rated MA.

www.fanfiction.net/s/3927981/1/Simple-Kind-Of-Life
Simple Kind Of Life
By: sleepymuse
Changed from dog fighter Kagome leaves the feudal era for a normal life, but her guilt makes her return. The well sends her to another world where she finds Sesshomaru and she brings him back with her. A slip makes her claim them both. SXKS
Rated: Fiction M - English - Romance - Sesshomaru, Kagome H. - Chapters: 26 - Words: 40,240 - Reviews: 230 - Favs: 208 - Follows: 87 - Updated: Feb 22, 2008 - Published: Dec 4, 2007 - Status: Complete - id: 3927981

or you can use this link:

inu.adult-fanfiction.org/search.php
Changed from dog fighter SessxKagXSess Complete
by patricia7dawn
its AFF.net so it's MA+!