Caught my bf watching porn

I recently caught my boyfriend of almost 2 years watching porn. At the beginning of our relationship I told him I didn’t want him watching porn and we both agreed and both said we consider that cheating. So my best friend also caught her bf watching porn and I told her my bf doesn’t do that anymore. I spoke so highly of him and I looked at his phone cause why not I have nothing to worry about. I looked and there it all was. Later that night we talked about it and he said he never watched it that he only went on the website to see what they had which was clearly a lie. I had the screenshots of the porn he watched. I don’t know what to do because he said if we were caught cheating than we break up. Should I break up with him? Please help I’m so heartbroken right now.