Besides the porn, he hasn't been honest- and switched from"I'll stop" to "it's natural". Not only that but disregard to your feelings (imo at least).
That there I believe is an issue but that could just be my interpretation..., as relationships are to be open honest and growing (in my opinion at least, everyone has their own view thou).
like another poster mentioned- i believe- it's something you have to decide if it's a deal breaker.
Could try counselling if you believe that may benefit you both and the relationship... Could try again to talk, in general about it.. could weigh this in with all other aspects of the relationship.
I'm so sorry that your having to go through this, and with so many posts about how porn is so great & the debate- derailing your individual situation.
I'm sorry I don't have much to offer but with great sympathies I hope peace can be again & that resolution is found.