I thought I was addicted to my bfs butt

I (32F) am in a relationship with my bf (26M). In all my previous relationships, the sex was very vanilla and I’ve always been satisfied by it. About a year into our relationship he confessed to me that he was very much into anal play, being on the receiving end and wanted to share that part of himself with me. At first I was nervous and apprehensive, but it’s become all I want to do. I cannot get off without using his ass in some way. I haven’t been on the receiving end of penetrative sex in months because I no longer have a need for it. I’m genuinely obsessed with, addicted to his ass. We communicate well and I know that we are both satisfied with our dynamic. That’s not the issue. The issue started when I noticed that I’m almost always distracted thinking about it and that I can’t look at him without picturing him presenting himself to me and we can’t be alone together (we live separately) without me needing to use him. We used to get out and do things together, shared hobbies and the like. Again neither of us was unhappy with this. But I can see how it’s changing/affecting my life. My real problem is it’s now the feelings and thoughts are extending to other men. I cannot interact with men I find attractive without picturing them in my bfs place. I was checking out at the grocery store this morning, there was a cute guy working the till and I legitimately went brain dead in the middle of my transaction because I pictured him with his pants around his ankles and bent over the till. I feel like a creep or a predator and I feel bad for taking something my bf shared with me and getting so incredibly carried away with it. Idk what I’m looking for posting this. I wish I could talk with someone about how I feel but there’s no one on my life I would share this information with.