No MarchLikeAnAnt, I think you have a low sex drive or are asexual because you're so uncomprehending of what you think the OP should be giving up, and so flippant in your response to her. And please understand I'm not judging you for whoever it is that you are. Just that I think your response (and that of others, now I've read a bit more of the thread) is oversimplified and lacks an understanding of what sexuality means to some people. As an aside, I had a very black and white view of sexual ethics when I thought I was asexual and didn't know what I was capable of. I'm not saying you are like me, or that you should be like me, but I think it's fair to say you don't understand what I would be sacrificing if I had to give up sex.
Offred, I absolutely agree that being traumatised by rape does not make one asexual. That's exactly the point I was making. For the purposes of this discussion, I don't think it matters whether asexuality is real or not. The OP is not asexual and it doesn't sound as though her husband is either - he's ill/disabled. Even if he were asexual, just because he doesn't need sex doesn't mean the OP doesn't. Celibacy is not the same thing as asexuality.
Would we all agree that friendship and human interaction are human needs? What would happen if you were suddenly cut off from seeing friends and family or socialising with anyone? Sexuality is much the same. After a good session, I feel calm, at peace, fulfilled and loving to the world in general. Nobody would expect me to spend my life alone in my living room without making friends or socialising just because that's not a direct cause of death. Why is sex different? Though actually, denying yourself human contact like that can have a terrible effect on your mental and physical wellbeing and can be a contributing factor of mortality.
I don't think having an affair is 'right' but I also don't think the world is utterly black and white. It is easy to say 'well leave the relationship' as if it's just putting down a rucksack. I can well believe the OP loves her husband and can't just leave him like that, but at the same time can't countenance a lifetime of never holding and being intimate with another person. I don't think expecting someone with plenty of life in them yet to give up one of the most life affirming elements of humanity against their will is right either.
DowagerCuntess, I absolutely love your username.