Some men make brilliant partners and dads.
But too many men are ill suited to domesticity and fatherhood.
They like the idea of it; they marry the fun, carefree, slender girlfriend, expecting it to be like that forever.
The first pregnancy happens - and suddenly everything's changed. They are no longer the centre of her world.
Her mind and body change and suddenly she has a purpose and intent that is not centred around his needs.
The reality of pregnancy and childbirth (which my mother tells me was absolutely not a place for husbands when she was having us) probably terrifies and horrifies them - but they can't express or explore that.
They have no control over this absolutely female process - and problems start.
The reality of newborn, toddler, tween and teen can be a horrible shock - AND NOBODY TRAINS US HOW TO DO IT.
We're just handed an entire helpless new human and told 'Parent that. Bye'.
Anyway.
Yes, it's possible that while you've been preoccupied with childcare, he's developing a lightearted relationship with a work colleague that feels nicer than home.
But it's also possible he's knackered and feels low.
Don't immediately jump to conclusions.
Don't sweep out.
Don't do the silent treatment.
Ask, give space, listen.