Is it normal that i can't stop masturbating to this?

I have always been the kind of girl that gets nervous, fearful, worthless and jealous of beautiful girls and I have trouble overcoming those feelings especially in their presence. I started my first relationship several months ago and my boyfriend mentioned that 2 girls from his high school were playboy models and he followed them on instagram - my heart fell and my first thought was I had to look them up. One of them was so beautiful I found myself fascinated and stunned. Everytime i looked at her picture, i felt dizzy and I couldn't focus. I now can't stop looking her up online everywhere and follow her instagram page religiously. I have been masturbating to her pictures several times a day, thinking about how my boyfriend feels about seeing this beautiful girl from his school half naked, sometimes for several hours a day. She gets so much attention from everyone and her lifestyle is so tantalizing. I think why I'm posting this is to hear from other women or men who have felt this way and how they overcame it. I'm too embarassed to tell anyone. This is affecting my sex life with my boyfriend because I feel like I can't get off unless its about her. How do I overcome this?