Hello and thank you for your question.
There are still too many unanswered questions for you to have clarity on this situation. And though he claims he only met one person for coffee, he has still betrayed your trust by his activities. And it's possible that he is not being honest as well about not seeing more women, etc. The fact is that he has broken your trust. I disagree with your friends who tell you to put the past behind you. That is not addressing the situation and this is indeed a situation that is quite present, and needs to not just be overlooked. If you do just put it behind you then it is quite likely to continue. So, what needs to happen as you say that you really don't want to leave him, is that you both need to get counseling together. This way the therapist can help him be honest about everything and you can get the answers and clarity you need. The therapist can also address why he did these behaviors, and how likely he is to repeat such. He will need some additional counseling as well (on his own perhaps) and you can have your couple counselor determine that as needed. But for now you both should go together. Even though you can only prove that there was just one person at this point, you still have plenty of evidence that he was betraying your trust with all of his online activities etc. And that is enough to warrant the counseling. The rest can come to light once you start counseling. It is a must at this point. Call your doctor and ask for a referral to a good relationships counselor in your area. It's good that your boyfriend is willing to get some counseling, and you two can begin right away. Please click ACCEPT, otherwise I'm not paid for my assistance. Or ask for more info. Thank you.