Dealing with the urges

I’ve been addicted since I was 12 to porn. I’m now 21 and trying to build a career. I need to quit. I’m so motivated to quit. But I sit here doing school work and a random sexual thought will pop up in my head and I can’t get it to go away. Unless I dull my brain out with other non explicit content like a movie then I cannot focus on my work. It’s really becoming too time consuming not being able to focus when I get these urges. Does anyone have any advice on how to quickly move past these urges and refocus on the work in front of me?