Hello, thank you for allowing me to help you with this situation. I can understand how stressful this must make you feel. In a sense, this is not unlike discovering that your partner is having an affair. Indeed, the situation bears similarities not just in the fact that your boyfriend is directing his intimacy towards another partner, but also in that he has felt the need to lie and cover it up. One possibility that you cannot rule out, is that your boyfriend has been also physically involved with other partners, either male or female. I don't raise this point to distress you, but to call attention to the need for caution as regards transmission of STD. More generally, my sense is that this situation raises an alarm as to the condition of the relationship. My biggest worry, frankly, is not so much the pornography, as the lack of communication around this issue. You have described a pattern of mistrust and secrecy on both sides--you felt the need to monitor his computer; he hid his activities; you let your initial concerns drop quickly; you let the most recent conversation go despite your real concerns. I don't say this in any way to lay blame--this is a difficult and stressful moment for both of you. But I do want to emphasize the communication lapses at the heart of the matter. I would not let yourself get detoured by the fact of the porn so much as focusing on the real crisis, which is the failure to know your partner or for him to know you. This moment could become a blessing in disguise, if it motivates you as a partnership to wade into some raw, honest emotions with each other; whether that ultimately leads to break up or a deeper bond, I believe this will be a healthy step in either case.
Please let me know your response to this feedback. Very best of luck to you.