Starvingartist...I second what HDhusband is saying. Your husband sounds like he is truly LD. There seems to be a difference between partners who did have desire at some point in their lives but have stopped desiring sex for some specific reason or set of reasons, versus partners who are and always have been LD with no change over time and circumstances. Those who are truly LD have the hardest time changing themselves, and sometimes their HD partners do have to make that hard choice: accept having a sexless marriage, or leave. Sometimes an LD person simply cannot change enough to make their HD spouse happy.
It is not clear from your posts if you have ever made the direct statement to your husband or not, "I will not accept a sexless marriage forever". Maybe you are not sure yourself of your feelings on that. But from all the stories I've read here, usually it takes that type of discussion with the LD spouse in order to cause any change. The promises over the years of "it will change" or "its because of stress" and then no lasting change ever occurs, is a clear sign to you by this point that your husband likely will not change on his own. However, he may try a bit harder if he understands that you are willing to leave eventually.
Have you ever thought about having that discussion?
I would like to just say about him watching porn, that while it is very likely harmless in general, in a situation like yours, it is actually harmful (IMO). The reason I say that is that if he has precious little sexual energy to begin with, and then is using that limited energy by himself, then will not be any left for him to use together with you. He is wasting it, so to speak. And further, while using it alone with himself, he is not learning more about his body, about your body, and about intimacy. Instead he is learning about a quick, detached release, and his body only knows about this type of release if he's not practicing together with you. If I were you, I would bring it up. I would get into a sexual mood myself, at a time when you know sex is an option, and then say "hey hon, I've noticed in the history you've been checking out some porn...care to share some of it with me?" Then hopefully get him to show you what he's been watching, watch some with him, encourage it to lead to sex...and hopefully later, talk about it some more. Invite him to share more or at least discuss things with you. Segue into a sex discussion in general.