This is the way I see it. You gave him permission to use porn, you DID NOT give him permission to use you though. Porn can be used without him dismissing your feelings and I have to tell you this from my point of view. The guy would have to be a Neanderthal if he didn't know that making love to you up to a certain point and then finishing the job with porn is a HUGE dismissal of you as a partner and a human being.
He needs to separate the two things...his relationship with you and his porn, they are not one in the same. I can understand your reaction. I can't think of anything more gut renching to realize that you were good enough for the start but not for the finish.
If he is unable to orgasm with you then he needs to step up to the plate and communicate this with you so the problem can get worked out. What he is doing is damned hateful in my opinion. He has problems, is refusing to face it and you are taking on his problems with all this anxiety you are feeling. The sooner you realize this the sooner you will get a handle on all the negative self-talk you are doing. Cathy