But to me, it makes me feel unattractive compared to what else is out there and being shown, and it makes me have low self esteem.
Dealing with the onslaught of commercialized images of female beauty and sexuality can indeed be hard to deal with, especially if we're not as confidant about our own beauty or sexuality as we'd like to be. However, it sounds like you're trying to force a fairly extreme position regarding images of female sexuality on your fianc� by giving him this "my way or the highway" ultimatum. Surely in a healthy relationship where both partners respect each other, he should be willing to listen to your wishes and honor them to the degree that he is comfortable with, and it sounds like he's trying to do exactly that. But it sounds like that this just isn't enough for you.
Perhaps what you should be doing is asking yourself
why you find these images so upsetting? I have ethical issues with some of them myself, as does anyone who thinks clearly about the effects that the exploitation of female beauty and sexuality for commercial purposes have upon our youth. But it sounds like part of your problem with images of female sexuality isn't so much that you think it has a negative effect upon youth as it is that you personally feel threatened by any image of a woman who is more attractive than you are, even if that woman is a cartoon. And while it's certainly natural to feel less than confidant if your husband or boyfriend is constantly ogling other women, you shouldn't feel quite this threatened by it unless there's something else going on.
The fact that this issue has brought you to the point of considering a breakup of your relationship should be a big red flag to you that it's time to seek professional help. I would recommend seeing a therapist to discuss your issues with this and hopefully resolve some of them without resorting to threats of ending your relationship. If your fianc� truly values your relationship, he will be willing to work with you on finding a middle ground regarding what you perceive to be gratuitious sexuality, but don't expect him to put on a blindfold for the rest of eternity.
Above all, keep talking to him about your problems and your progress. If you look at him as your
partner rather than as your
opponent in this issue, you will be more likely to resolve things in a way that both of you can live with.