Recently I heard someone talk about how guilt and shame are not the same thing, although the context wasn't porn.
Let's say you are at a friend's house, and break a dish. Guilt tells you that you broke the dish. You apologize, you may offer to pay for it, you may replace it, or you might make some other gesture. Shame tells you that you're an awful person, a klutz, and no one would ever want to have you over to dinner ever because you ruin everything.
Guilt is knowledge of having done something wrong, or still doing something wrong. Shame is feeling like you are less of a person because of it. Guilt can be a good thing, because it just means our conscience is working, and we recognize bad things. Guilt may make us want to correct past mistakes, make amends, or offer atonement. Shame, as far as I can tell, never really accomplishes anything. Shame just beats you down.
So, remember these feelings and know that what is making you feel awful is porn. It isn't because you're a bad person, or gross, or a loser. Porn makes you feel that way. So, when you feel awful, what do you do? Find more porn! Then you feel more awful, which means... well, you get the idea.