Please help

Is it wrong for me to want my boyfriend to stop watching porn? I posted this earlier but deleted it due to lack of details in my post. Anyway my boyfriend and I have been together for almost 9 months and I hate the fact that he watches porn. I've expressed my feelings multiple times to him about me wanting him to stop but he just keeps doing it. I've even sent him pictures hoping that maybe he would use those instead. I've tried talking to him multiple times and all he ever says is that "it's just porn" or he'll promise to stop watching it and then the next time I see him and check his history on google he's watched it again. I'm at the point to where I don't  know if I'm wrong for not wanting him to watch it or not and I need more opinions. Feel free to comment any opinions will be appreciated. :)