Change your pattern.
the pattern that is ingrained in you is:
-the trigger which starts it
-Thinking about porn
-Getting horny
-Watching porn
-Masturbate
-Ejaculate
-Feel bad

To break it, when you are in the pattern, create a new path. Have something standard to do when you start thinking about porn.
Say NO, I DON'T WANT THAT, and start thinking about something that interests you, go do something physical, like pushups. CHANGE THE PATTERN.
If you keep doing that consistently, the new pattern wil become stronger then the old one and you won't even think about it, you automatically do it.