That is very common for those of us recovering from porn and masturbation addiction. I used to use it to get to sleep. Those times at night - or when alone at home with an unmonitored device; for me a big thing was my personal smartphone, so I traded it in for a flip phone - those times when you’re alone and waiting, or maybe doing something & you’re bored or frustrated - those times are hard.
First: you are not alone. There are a lot of us here (and a lot around the world) who are going / have been going through the same struggles. In my own case a big, big help was when I realized I couldn’t do it alone. I needed support from others also in recovery from this. I searched up and found a sex addiction recovery clinic in my city. Neal made a really good post of resources here:
Your addiction behaviour is there because there is something out of alignment at the moment. You have the power to work on the problem, and to change it. A significant help, is to find people who can accompany you through recovery. Do you have a group or a centre you can go to?