I'm sorry, but I fail to find the irrationality in you, Neicie. How is it irrational to expect reciprocity? Especially when it involves something that you may very well want MORE than your H? (we have the same problem from time to time: an aroused human being with unfulfilled sexual desires is NOT desirable, from both psychological and physical points of view...)
No, I think you're the rational one and he is, in fact, the one with the psychological problem. Obviously, Crohn's can play a role in this, his mental functioning may not be exactly what it was, and it is natural for him to focus on his own body and needs most of the time (I'm coming out of a chronic illness, the ill partner has to do what Michelle says and JUST DO IT unless of course they are completely incapable - which he obviously isn't).
I'd be really po'ed too. It's almost as if your husband is signalling that physically, he can ML when he wishes, but that it's entirely on his schedule.
Good luck with this. Will it help if he sees your irritation as part of a response to how attractive you find him? Surely, if he knows you find him so attractive, he'll see why it's a good thing not to "waste" opportunities for you both to enjoy yourselves. It's like taking a kid to Disneyland and making them wait outside while the grownups go in.
Oh, one more thing. I'm not sure I'd view your H's behavior as "hiding" behind his illness. It's just that when he does have good days, the number of different things he wants/needs to do must be quite large. It may not occur to him that sex needs to be a higher priority on those days. He needs to take charge of his illness cycle by asking himself (every day if possible), is this a good day or a bad day, and if it is a good day, is it a day when I might consider ML with my W? If he can occasionally feel ready and move ML to the HIGHEST priority on his todo list, you'll be much happier. Eventually, you should get a take on how often this is, and you could move on to other issues, like, is it often enough? You love him so much, I'm guessing that if you knew he was trying to make it a priority, it would be enough.