We have two kids together and one from my previous (starter) marriage.
But it is also possible that your husband has always been denying this part of himself and now, in midlife, he just can’t hold it back anymore.
Sexuality is a spectrum, though, so I think it’s something more fluid. I cannot even imagine how hurt you feel, but allowing yourself to pretend that a duck is not a duck will not help anything.
Your husband is attracted to either only men (read this site, it’s interesting although I don’t agree with all of it) or men and women.
Another reason is that I myself find this really disorienting and uncomfortable. But we need to figure out how to get through this while being true to ourselves, or how to separate amicably without hurting each other or the kids.” The book Is My Husband Gay, Straight, or Bi?
: A Guide for Women Concerned about Their Men can also guide you through other conversations and decisions.