[In a selfish way, he'd hoped the confession would make him feel better. But it didn't, he only felt worse for it. Maybe it was because, even experiment induced, a part of him knew how wrong this was and loathed being unable to express it.]

I thought I could ignore it... forget it happened. When you showed up, I mean, I didn't think I could just tell you about it.

[It would have crushed her. But not as much as it will now. A consequence of his selfishness at trying to avoid confrontation.]

... and I shouldn't have kept it from you. Because I didn't forget it. And I can't ignore it.