how can i overcome lust

hi. im a 16yo boy who is suffring from porn addiction .its started 3 years ago out of Curiosity i still fell the shame of my first video. last year i become closer to god and i cant let god look at me when im in losing agianst lust. last week i relepsed after 21 days the devil was calling to me to that room when nobody is watching im sorry god i couldnt make my promis. how can i quit pornographie for good is quiting gradually effective ?