A lot of your fears can be dissolved with simple conversation.
1) Those “fears/scary thoughts” you have should be discussed immediately. They will only cause doubt and will tear you apart.
2) The underlying reason of WHY he’s looking at porn is an unmet need. It doesn’t mean that if you aren’t that “thin white girl” that you have to become one, it means that you need for him to know what he wants, so he doesn’t have to go searching for it online.
3) Guilt is a factor, or he wouldn’t turn it off/hide it; he feels that you would feel inadequate because you’ve been together for so long, but he’s still turning to porn for sexual stimulation, rather than you. He doesn’t want to hurt you, but doesn’t know how to communicate that to you.
---As far as trying to become a sex slave in order to try to keep up with his sexual fantasies, forget it. You will always be playing a game of catch up....not to say that it wouldn’t work, it’s just that it’s a lotta work----and that’s time and energy that could be used more productively building the relationship, on more than just a sexual level.