I read this great fic a while back, and forgot to bookmark or favorite it. I can't remember the name of the fic, the author, or even what site it was on, but I remember the plot.
Sesshoumaru and Kagome have been together for a while, but Sesshoumaru is pretending to be human, because Kouga, her last boyfriend, was a youkai and got dumped. So he keeps fighting his inuyoukai instincts on how to behave with Kagome, and while it takes a toll on him, he's ok with it.
Meanwhile, Kagome (who knew since the beginning) goes to Sango for advice, because as a deamon slayer, she knows how to rile up his youkai side. Kagome goes home, uses these tips, and even though he put up a valiant effort, he ends up giving in and licking her. She then admits that she knew all along, dumped Kouga for totally different reasons, and Sesshoumaru finally allows his instincts out, which ends in some smutty resolution.
Thanks a bunch! ^-^

I think it might be This Sesshoumaru Does Not Do Christmas by SunsetMiko that you're looking for. She's an active member of dokuga so you shouldn't have trouble finding this fic

Hope this helps

~Fuyu


EDIT: So I went and checked and I'm pretty sure it's the one you're looking for. Here's the link: www.dokuga.com/fanfiction/story/1245/1

That's the one! Thank you!