You could start with some reading about what is happening to you and your brain when you watch porn. It is most likely something that you never thought about. I think once you get some understanding of what is going on it might help. Then try 90 days no PM but only worry about it one day at a time.
Also find another outlet for your stress. A lot of people exercise instead.
Think about the industry and what it is doing to those people. @DungeonMaster posted this article:
Try to figure out why you are do this other than the obvious relief. Change your habits and routine. For me it was ritualistic. Same time every day but then it grows.
Maybe go to therapy with someone who specializes in this issue. Or find an SA meeting. It is a little uncomfortable at first but you will find people struggling with the same things.
Also keep coming back here. Check in and read. There is great support and motivation.