How do I get him to confess he went on a date with another girl?

So, I just told the guy I've been dating for four years that my friend saw him with another girl our somewhere. But in reality I saw on fb that they both went out together. They used to date a few months back when we were on a break. He denied the whole thing that they went out together while he and I were dating. He told me my friend was lying. I said well I know your lying because I know you two went out together. Never told him how I found out. I tolf him the only way I would keep dating him is if he confessed or if he would call her/text her or if I could so I can get some answers. He said he would never contact her. I said';why is it because your lying to me'; he said he has nothing to prove and he isnt going to go thru my little hoop. Am I out of line? I really believe I deserve some form of explanation as to why they went out together. I told him if he wont contact her or let me then I'm never going to talk to him again. He said fine. BTW he has cheated on me twice in the past. he always talks to girls on online dating sites but says he isnt anymore. What do I do?How do I get him to confess he went on a date with another girl?
';Once a cheater, always a cheater.';



Either end it with him, or settle for someone that may never be faithful to you.How do I get him to confess he went on a date with another girl?
huhhh. What an ***! No real boyfriend would EVER, i repeat EVER do that to his lady. You really need to get off yahoo and DUMP HIM!