I'm pretty sure it's Baby Got Back. It's NC-17, so no YIMs.
Baby Got Back by Scarlet Reviews
Kagome gets injured in the past and is bed ridden in the future causing her to gain quite a bit of weight. Now she must face her friend's and worst of all Inu Yasha. Ever wonder what youkai looked for in a woman? (warning...this story may cause weight gain)
Rating: NC-17 - Universe: Canon - Status: Incomplete - Genre: Humor/Parody
Updated: 05-15-06 - Chapters: 8 - Reviews 170 - Words 8,802
It's also on MM if I recall correctly; it may be more complete there.