@FunTraybake it doesn’t sound like your relationship is in the healthiest of places if he’s refusing to discuss issues, quitting his job will though telling you, going awol but ignoring it in return. His lack of communication is actually really disrespectful to you and your children. This is not the behaviour of a good partner or father.
The cause of his behaviour could be any number of things (depression, an affair, work stress, lack of emotional growth due to parents) but none of it excuses how he is treating you. You deserve better.
You are clearly and understandably in a state of shock. Is there someone IRL you can speak to? You need to give yourself some time to process and understand what it is you want for your life moving forward. If he returns home again in a day or two are you going to let things go back to normal til the next time he decides to leave? It’s not fair on you or your DC to live in this uncertainty. Living with a man who has taken off 4 times in a year without explanation sounds extremely stressful and unsettling for all of you.
If he has left for good (or you decide this is the end of your relationship even if he does want to come back) then you need to start processing your feelings as well as taking practical steps to protect yourself.
A husband who has left is no longer your friend and ultimately cannot be trusted to be kind, moral or predictable (other than in the sense of being like every other man who has ever left his wife in that he becomes a prick).
I’m so sorry you are having to deal with this. You can get through this, you are stronger than you know