It would probably be easy to call you a shrew like you said, tell you that since your husband had cancer you should be so considerate, and condemn you ...
But I'm not going to do that.
You have a need that is not being fulfilled in your marriage and when people's needs aren't fulfilled, they have a right to be upset. Talk to him about the severity of your needs and do what you can to take care of them yourself. Is masturbation out of the question? Toys, vibrators? His lack of sex drive isn't his fault; it's just how his hormone flow is going, but you should be able to compromise in the middle without infidelity coming into play. If you can't, then you should consider whether you could spend your life celibate, whether you could justify cheating on your husband, or whether you wanted to divorce him over this.
ThePhotographer ... your answer kind of makes me sad. I read the thread you posted a while back, and I assume those issues have not been resolved? I hope you can find a way to be really happy with your sexual life :/ You seem like such a caring person.