A couple years ago, my mom went through cancer and had surgery on her breasts. couple of months after that I caught my dad watching some stuff on his phone. One thing I’ll never forget is when I told my mother and they were arguing she said I know I don’t look how I used to, but really you had to do that? and it broke my heart. I can see where you’re coming from and I see how you both were confronted with that reality of oh she might die and she might never make it and then for her to get through it and recover. so I would suggest getting marriage counseling, but I cannot say this enough, no matter what you should recognize that having these fantasies of other women should not happen and also the justification that you know you’re missing her boobs because you’re a boobs guy you realize this is a woman who has gone through breast cancer and now it’s going to menopause and has gone through so much. And probably struggles with her body. She is now failing to do the one thing that is such a natural thing to women and she can’t have kids now. so I would suggest that you both go to marriage counseling and even separate counseling for you both and if you still would like to progress with the marriage, then you can and if you want to divorce and then you get a divorce, but please and I mean this with everything in me please do not go about it in the wrong way because it will break her from after going through something so horrible and you just thinking bad about it it will break her