Actually I went through this in my story "Burden of Guilt" for Inuyasha fanfic. Inuyasha knows who he wants in his life from the time that he was almost dragged into hell. He tells Kagome about this several times in the manga. He feels an enormous guilt towards Kikyou because he feels responsible for her death. As a result he feels that he feels that he is not entitled to be happy.

People forget that they were killed on what was to be their wedding day. (Romeo and Juliet) Each of them thought that the other had betrayed them. It is no wonder that when Inuyasha was revived and Kikyou was resurrected they were still angry at their betrayers.

One of the most interesting lines in the entire manga is in Jealousy. Kikyou is trying to explain why Onigumo wanted Inuyasha dead. Kikyou explains that Onigumo was jealous of Inuyasha. This baffles Inuyasha who cannot understand why anyone would be jealous of what he had with Kikyou and she agrees that the jealousy was ridiculous but so very human of Onigumo.