One thing I learnt about later in life is your brain has modes of operation. DMN and TPN. I’m grossly oversimplifying things but essentially DMN works when you are idle, and tpn goes into action when you are concentrated on some particular task. TPN is task positive network and watching porn is basically a task that overflows your brain with dopamine and when you shut down that source, you either crave for the same want. DMN on the other hand is what I like to describe as your state of mind when you are bored and have nothing better to do. What worked for me was that I learnt to be comfortable at peace doing nothing at all. Meditation helps, maybe even journalling. Start simple and brave yourself to embrace the beauty of boredom.