I have read through your posts here and am sorry to say I agree with the respondents who say you are in denial about your husbands sexuality. You are asking variations of the same question over and over again, I would assume hoping for a different answer that would put your fears to rest. I understand that you have a strong desire to know why he is having sex regularly with men. Consider this: would you prefer that your husband were abused instead of gay? I'm sorry is that question is painful.
What are you doing for you? Even if you choose to continue trying to find another explanation for your husbands preferences, he is cheating on you repeatedly over many years and with many men. I dont know When you found out, but you know about it and presumably tolerate it. You might want to begin asking yourself why you are willing to tolerate this behavior in your marriage. I hope you've had a full work up for STDs, including HIV. If you feel you are not at risk because of a lack of sex on your marriage, then you have another piece of the puzzle. You should still get the tests though, if you have had even a single encounter with your husband been he's been having sex with other people. It only takes once.
Even if he was abused, which he says he was not, he is making a choice to step outside his marriage for physical intimacy. Is this OK for you? I don't think so since you are desperately seeking answers.
You might want to think about going into therapy for yourself to address your issues around this and determine the sort of marriage you want at this point in your life and whether you have that with your husband.