Yo man, I'm this journey with you! Don't beat yourself up when you relapse. Recognise what got you to that stage and make the necessary changes to avoid it next time.
Figure out your triggers. Is it boredom? Loneliness? Once you have your triggers figured out, do something about it. Make changes to your daily routine if necessary. You need to transmute that sexual energy into something positive. This could be exercise, learning a new skill, indulging in hobbies etc. Find your passion and put your heart and soul into it.
If you feel tempted to relapse, jump into a cold shower. Go for a run. Do push ups till you can't no more. Do anything to get your mind off of porn/masturbation. You've got this man, I believe in you.
For the record, 28 days is f*cking dope. You should be proud. You've relapsed, but that doesn't mean you've lost all your progress. Just make sure you don't binge. Now go man, go and prove to yourself that you're a warrior who never gives up.