*hugs* I'm sorry that you're hurting. I've been married for 27 years. I've known my husband for 34 years. These are the things that I've learned:
1. Your marriage can Change. You can make your marriage what you want it to be (If both partners that have no addictions, substance abuse, reasonable mental health, etc.)
2. Prayer changes things. Acknowledge Him in all your ways and He will direct your path.
When we were first married, hubby had a collection of playboys. I was so insulted by this, I felt cheated, abandoned, degraded, etc. I didn't think I'd ever overcome his posession of them, even though whenever he was accessing these materials was a mystery to me. We were always together and had (still have) a healthy sex life.
I think the key issue here is the quality of your relationship with your husband in general. Are you best friends? Does he make you laugh? Do you enjoy your time alone with him? If these factors are present, then overcoming sexual issues can be accomplished with relationship work, counselling, etc. If these factors are not present, then it seems to me that you've got more important issues on which to focus your energies.
I was ready to leave my husband once. I moved in with my sister for a couple of months. I was drenched in self-pity, feeling like the relationship was all give & no take. I wanted deep emotional support, romance, the sense of connected-ness that we had lost. I went through years of feeling like nothing would ever change.
But then I realized, my problems were not his problems. My emotional needs, my wounds were my responsibility to work through, instead of relying on him to heal me, or make me feel better. I prayed. I did some deep thinking about why I felt so unfulfilled, then I worked on learning to appreciated my husband for who he is. I also realized that NOTHING is greener on the other side of the fence.
I came to understand that many men are literally burdened with sexual thoughts. Their interest in looking at girly pictures is nearly a reflex, not even a conscious decision. I'm not making excuses, I'm just stating that in this culture, it's pervasive and they've been raised to believe that there's nothing wrong with it. 'Harmless' is the typical phrase.
Now that so many years have passed, I see my husband's sexual thoughts and sexual intimacy as two entirely different things. His interest in a pretty girl on the street or his favorite actress has nothing to do with his sexual feeling for me, his desire of me, his appreciation of our sexual intimacy. He's a man, he has sexual thoughts, I'm a woman, I have sexual thoughts. What we bring to each other in the bedroom is more than sexual release. I no longer relate his interest in pretty women's pictures to me at all. I am his jewel, his prize, his treasure. He chose me, the most perfect bikini babe could never compete. It's not about bodies anymore.
How did we survive 27 years? It relies on both people always placing each other's needs first, continually.
I hope you find the answers that you need. I will pray for you and your family.