Hello there.
OK, there are many different interpretations of this. I completely agree with the posters who say that this is not the way to do things, as an adult, with children, in a relationship with someone you are supposed to love. The adult, rational way to do this would be to talk about things being difficult, to name and address difficulties, and to organise stuff so that you and your partner can give things a good go at getting better.
Staying quiet and then reaching for the nuclear button is just foolish. Or cruel.
So, it could be him being a bastard, it could be that he has met someone else ( you would be amazed at how many, apparently sane and reasonable people convince themselves of all sorts to justify having become interested/involved in someone else), or it really could just be the sign of someone failing their NVQ in Adult Emotions and Relationships.
The Way Forward:
This only works if you are both committed to trying to make it work. It won't work if your dh is actually using this behaviour/announcement as a way of controlling you whilst simultaneously ensuring he needs do no emotional labour in your family life. it is really, really important to establish what's going on.
You go for counselling.
You really do spend time together. Proper time.
You work on re-building intimacy, love and trust.
There are various "techniques" and activities for the latter, but a good counsellor will lay them out for you.
It souns simple, but it really does require effort, and resources of actual time and money being laid aside for the two of you. Which is quite a commitment in many families. In theory, it can cost nothing - but, to be honest, it will cost you in babysitting if nothing else - and counselling fees.
However, none of this will work unless he is actually hoping to make things work. As well as you.
Agree with all the posters who say that you really should watch out for letting this turn into a case of you jumping through hoops to make hime happy. This can happen, and it is no life - and I would say it is the express highway to an emotionally abusive relationship.
Good luck.