It sounds like "Misconceptions and Misunderstanding" by Time on my hands. Sesshomaru marries Kagome but on their wedding night finds no "barrier" and concludes she's not a virgin. He sends her away from his room to live in another room of their house. She's depressed. An eventually he learns the truth from Inuyasha. Once he finds out she had cancer he tries to repair his mistake but Kagome has sunk into depression. He takes her on their missed honeymoon to a deserted island but there is a storm. He gets a head injury and forgets all the bad things that have happened. Try
www.fanfiction.net/s/4969113/1/Misconceptions-And-Misunderstandings
EDIT BY WICCAN: This story is rated MA, NO YIMs!!