It's a story I read before a long while back but I can't remember where I read it or the title.

From what I remember, the jewel is completed and it re-merges with Kagome which makes her immortal and nearly unkillable. Either Sesshoumaru decides, or he's told by Midoriko or a kami, that he is to be her protector and mate or something like that. And he was blessed or something so that her miko powers can't hurt him. So he takes her away and forces her to be his mate and he's really mean to her because she won't agree to it. I think he locks her in the dungeon or something. She makes some sort of deal with him that she will be his mate but she'll never speak to him or anyone ever again. He's still really mean to her and has a short temper and get physically abusive with her but eventually she discovers she can use barriers against him. And thats about all I can remember. I do remember something of their relationship beginning to repair and get better because he starts trying to be nice.
It's been such a long while since I've read it that I can't remember much of it.

That might be Stirrings of the Blood by Shabopo. It was never completed, and was pulled by the author (I think because of a few too many plagiarism attempts).

Edited...

I was wrong, darkmousey is right.

Aww, that makes me sad. I hate when that happens to a story I like. I've had worse happen though, I had an author die before finishing her last chapter once.