It sounds to me that he is embarrassed, not necessarily that he is hiding anything horribly wrong. He feels reluctant to talk about it because it is an embarrassing topic although it seems that you are really handling it well.
Another thought - you mentioned you have an outhouse. Is it possible that he is afraid to go to it alone?
I hope others will have better advice for you.
Another thought - you mentioned you have an outhouse. Is it possible that he is afraid to go to it alone?
I hope others will have better advice for you.