Having read this whole thread this evening - it was a long read - I'd just like to add a few comments. Some of these may not be very popular with a couple of the very strident anti-men posters on this thread.
Through my work, I have come across some obsessive collectors - although I must admit the largest was only about 6,000, not 14,000.
You mentioned that your DH is very obsessive in a number of his other hobbies and I would suggest that with this porn collection, the word ''collection'' is more important than the word ''porn''.
Men - and it is generally men - with this sort of obsessive personality can easily go from an ordinary interest in a subject to a quite obsessive collecting interest with relative ease and without realising that they are doing it. I would strongly suggest that his interest in such a large collection relates more to him collecting the ''entire set'' of a particular actresses photos rather than primarily using this as material to use for masturbation.
Think of him as similar to an obsessive stamp collector, but with porno pictures instead of stamps and I think you will get nearer to his real desires and motivations about having such a large collection.
I would suggest that, in his mind, he probably does not see it as cheating on you or demeaning you in any way but simply an expression of his obsessive nature.
Now, I am in no way trying to say that what he is doing is in any way justified, I'm just trying to, perhaps, shed a little light on his motivations.
I don't know how well you have articulated your feelings about this to him in the past and, I would suggest, that it is likely that he doesn't yet really understand the effect that this has on you and why you feel the way you do.
Might I suggest a couple of things and, if they really don't work then I would strongly suggest that you need to get some outside counselling, both together and individually.
Perhaps start off by asking him if he understands how you feel about this and to get him to actually verbalise what he believes you are actually thinking and feeling right now. You might be surprised at how little he understands your feelings, as some men like this can find it very difficult to really understand things from another person's point of view.
This will give you a starting point to make it clear to him how this affects you. However, this may well not be enough to get him to understand so I would suggest doing something further. Go online and get some pictures of gay porn - there are lots of pictures of really cute naked guys online with huge erections. Don't bother with regular porn, go for gay porn, that's where all the really cute guys are - trust me.
Download some of these pictures and then confront him with them and ask him how he feels about you looking at these really cute naked guys with huge erections while he's out at work.
I would suggest that he won't be too happy about that. Get him to verbalise - actually talk out loud - about how he feels about you doing it and then that will lead on to a discussion about how his viewing and collecting is affecting you.
Finally, I really would say that you would really benefit from dealing with some of your own self esteem issues as you do seem to put yourself down quite a lot which is definitely not a good thing to be doing.