Hello lady!
I've been reading your post and I feel your hurt and frustration. I know I cant really compare to me, because I am in a 1yr relationship, you are in a marriage and they are different! But well I posted ages ago about how my boyfriend couldnt get erect, and what people thought I could say/do to make things better, or what action we could take. And loads of people were really helpful, but there were loads of people posted stuff like "maybe he's bored. Stick your finger up his butt... Play with his balls" or "watch porn together" and stuff and it just didnt strike a chord with me cos what I like to think is that he wants to sleep with me because of who I am, not how much of a porn-star act I can put on, and it just kinda insulted me. Cos with him he doesn't have to pretend to be anything - my attraction to him just comes naturally. I like to think its the same with him.
In your position I would feel very hurt, because i'd be wondering why he can get off to porn, but cant get off to me. But you know what? It doesn't sound to me like he's gay. And it sounds to me like he is very defensive and sensitive because he has an actual problem. I guess when he's watching porn there is no scope for failure and perhaps that's why he won't sleep with you - fear of failure. But whatever the problem is, he needs to sort it out because it's not healthy and it's hurting you. Maybe he just doesnt realise the extent. You need to communicate these things to him. When you tell him its the porn or me, he has to know why... Why you feel this way. How it makes you feel and how you think it affects the relationship. And you need to make him face the fact he has a problem because otherwise he's just gonna stick his head in the sand and pretend nothing's wrong. If he doesn't respect your concerns and your needs and your requests, kick his butt, I swear to god, cos he cant treat you this way.