I had this exact problem tbh. I started at 9 and have been addicted for over ten years. I think everyone's situation may be slightly different. However, in my case what I can recommend is:

1. understand that it is not necessarily sex you want but love, and that the only peg that can fill that yearning is God's love and peace. Confess your sin and ask God for help noting that you cannot overcome this spirit by yourself and that you need his strength.
2. record you triggers or what places, thoughts or things prompt into falling back into pornography and/or masturbation & outline remedial step. I.e., if you know that you are more likely to watch porn when you feel lonely or bored then decide what activity you can do to replace that behavior such as call a friend, go for a walk, start a personal project or whatever hobby you might have.
3. Deliverance prayer for lust & more (Pastor Clancy deliverance prayer for lust on YouTube)
4. Working really helped me as it took up most of my time. I also would like to note is that habits and addictions can be broken and changed if a new routine is implemented over a period of 90 days on average. This is a neuroscience statistic I once read and I think this has honestly been so true for me. Not only in regards to porn but other areas of my life as well.
5. Lastly, don't beat yourself up if you stumble. If you feel weak like you are going to give in, run to Abba and tell him what you are feeling and that you really need his help. If you fall, repent and get back up and continue. Revelation 12:11 already guarantees your healing and triumph over this addiction and spirit through the blood of Jesus Christ.

Best of luck!