looking at naked girls

What’s everybody’s thoughts on your partner following naked girls on social media, like they post pictures watch their snapchat videos of them playing with themselves? Ive now told my partner 4 times to please not do it but he always does and it breaks my heart. I personally wouldn’t ever do it as i don’t feel like i need to see that when i have him, it makes me feel physically sick. It’s now always on my mind and it’s kind of killing our relationship. am i crazy or dumb for being like this?