Why do you relapse? Do you just believe you always relapse so what's the difference? Seems you've gotten used to just living a life of constant relapses to the point where relapsing is just a part of your life. You probably don't even feel that bad when you relapse anymore, you just come to expect it.
You need to get more upset when you relapse. You keep telling yourself you want to quit. You see no benefits to continuing watchin porn, yet every few days you watch it. What the fuck man? How are these relapses helping you beat this? They are not. Get a grip dude. You need to end them, get pissed off when you relapse! Don't just go about your business. Get angry at porn for having this control over you. Porn owns you man.
Figure out the REASONS you gravitate towards porn, then eliminate them! For example, are you just wathing porn because you're bored?! Are you sad? Whatever the reason may be, discover OTHER ALTERNATIVES to solve these problems... bordem doesn't mean go watch porn.. it means find something to fucking occupy your time... open up a book, learn a new skill, go work out, hang out with friends/family... play the guitar... ANYTHING YOU WANT.