I saw on some TV documentary we are all programmed to be both faithful and to have a "roving eye" at the same time, I truely hate the fact that I've always had some interest in other women, however fleeting, even when I've been head-over-heals with my partner. I see it as a very primative part of my brain doing battle with the more advanced civilised part. I'd take more notice of his rational choices than fleeting emotional reactions to his ex.

Accepting that there will be some interest in others is probably essential to a lasting relationship unless each partner keeps it secret so it never becomes an issue, but I suppose it's a matter of degree, how much is tolerable.

(I hope this isn't disturbing to you, I'm not that experienced with realationships so may not know what I'm talking about)