Sexuality is only complicated for people who are unwilling to be honest with themselves.
Look. I can identify as Rebecca of Sunnybrook Farms all day until I'm purple and fuchsia, it doesn't mean I actually am Rebecca, nor will I ever be.
You get the point?
A man who calls himself straight because he has a wife or a girlfriend, yet the overwhelming majority of his sexual partners are men, well, he can identify as straight until he also turns purple and fuchsia. However, the math doesn't quite add up.
It's really not that complicated.