Problem with nighttime urges

Hey! This is my first post here. I've been trying to quit porn since the year began, but I've been having a major problem that's preventing me from building a long streak. If you knew me in person, you'd think I was on a 500 day streak. Ever since I deleted all my porn accounts, I haven't looked at anything NSFW in two weeks. The problem here? I don't even need to look at porn. I can just imagine a pornographic scene and I go to town. These thoughts especially come up in bed, so much so that masturbating to these thoughts have become part of my bedtime routine. I wouldn't have a single NSFW thought during the day, but I would relapse just 30 minutes after I lay my head. This is the only thing holding me back, and it's a thorn in my side. Does anyone have any advice on how to suppress these thoughts, even though they've become a nighttime habit?