Fiancé watching porn

So my fiancè has told me before that he watches porn and I’ve tried to over look it but lately it’s really been bothering me, so one day I saw that he had watched it on his phone and left it up. I confronted him and told him how I didn’t like it and he assured me he would stop. A few days later, I went on his phone today and he had cleared his browsing history. I feel like he is still watching it and is trying to hide it.. what should I do?