from what you say, and from my own perspective as a man who was abused as a kid - starting at age 5 and lasting until 13 - and fogotten/repressed/denied for years - there is no doubt in my mind that he is alluding to having survied CSA - child sex abuse.
i agree with Tyler. as male survivors - this is about the most difficult and painful and scary thing in the world to even imagine doing - reveal a terrible secret that we have devoted our entire lives to hiding - especially to someone we are close to and fear losing.
you are in a very difficult situation. if you want to stay with him through what is likely to be a rocky journey, there is a delicate balance to maintain. and the circumstances will keep changeing. it will not be easy. everything is likely to be affected.
what he needs right now is to feel reassured that you love, support, accept and trust him. that whatever dark revelations he discloses, that it will not change your love and commitment or the way you see him. i was deathly afraid of being judged, dondemned and rejected - and therefore didn't tell anyone for decades. one of the greatest things in my life has been that my wife has loved me and supported me and stuck with me through the chaos and pain and hard work of treatment and recovery.
so - IMHO - the message that needs to be communicated - is that you care about him, that you are willing to listen whenever he is ready to talk, and that you will support him through whatever positive process is ahead. i would encourage him to get qualified, experienced help from a professional therapist. that may not be something you can do immediately - but when the time is right. another big help for me - that i would encourage when possible - is for him to start participating in these MS forums.
my recovery has been a collaborative effort with the help of the guys and F&F of MS, my therapist, my wife, and faith in God.
AND - don't forget to take care of yourself. you have come to a good place - where there are others with similar experiences who can offer insights and resources and advice. but YOU may need professional support, too.
it is great that you are there for him, that you have found us, and that you are asking the right questions.
all best wishes for both of you and HEALING!
"the scariest thing about abuse of any shape or form, is, in my opinion, not the abuse itself, but that if it continues it can begin to feel commonplace and eventually acceptable."
- Alan Cumming, "Not My Father's Son"