To still be struggling so much

Although you ended the relationship, it sounds like he very much forced your hand and had someone waiting in the wings. I think that's a very different situation to someone just deciding they are done with a relationship and ending it. It was a very long relationship too. Your friends and family have not been very understanding, in my view. Maybe they are struggling because they see you as wallowing in your misery - I don't know. I don't think that you should be over this by now, but maybe it's time to seek counselling and find a safe space to explore your loss and betrayal and work through your feelings. Is that something you would think about doing?

He really shouldn’t have done that, and it just shows how irresponsible he is. Although that may also have been a coping mechanism on his part because he was struggling on his own?

Bottom line is you are being very mature and sensible (recognising that you are likely to make poor decisions after a few drinks) and you’re putting your children first.

Honestly, a year is really not very long time, especially when you are very much caught up in looking after small children and their daily lives. It’s natural that you are still struggling if you were actually hoping to try and salvage the relationship. You say he had checked out of family life before he moved out so be patient and now give yourself some time to grieve the end of the life you thought you were going to have. There is no such thing as a definite timeline. It takes as long as it takes.

And do take advantage of your family and friends support. I’m sure they mean to be encouraging when they are expecting you to be happier without him.
For now, try and concentrate on enjoying the good things.

I definitely don’t think you should rush into another relationship, but it seems sad that you don’t want to socialise with your friends.

Do they really only go out to clubs getting pissed and picking up men? If so, you need better friends!!

Surely you can go to the cinema/theatre/dinner/coffee with friends, assuming you have childcare?

Life is short and you need to be living yours properly. Find some pockets of happiness 💐

We have these views of getting over relationships. But it’s very different.
He may have been not satisfied with the relationship in some way and that does happen in lots of relationships for all sorts of reasons - people change/grow apart/develop different interests.
But when someone basically seeks out another relationship, in any way at all, they aren’t dealing with what’s happening. It takes two to tango, so there will have been things he was doing which were contributing to his own unhappiness.
They weren’t ‘fixed’ by moving on from you into another relationship. They are just masked. And glossed over with new fun times with a shiny new person.
But they are still there. And if you don’t recognise them, you repeat them.
For you, you did the right thing by ending things. You recognise that this was a long relationship with two children involved.
If two people find themselves at an impasse in a relationship, but work on it together, there’s a chance that they can save it. If they can’t, they’ve given it a chance. It’s very sad, but that is life.
But when one person switches it tends to be something they are trying to fix within themselves. And while they try to fix it with someone new, they are fixing nothing.
Look at the statistics on how second and third marriages fail.
I hope that makes some sense.

Not sure how old you are OP but please know this.
Anyone, man or woman, has who moves on so quickly from a relationship, especially a long one, learns nothing. While it may all look fun and shiny, the fact is that person takes their same, tired old crap into the next situation. At some point it rears its head again.
What you are going through now is actually the healthy way of doing it, even though it feels bloody awful. You are not jumping into anything, you are grieving the loss but in time you will have also reflected on what didn’t work last time around.
When time has passed and you meet someone you’d like to pursue things with, those reflections will be so valuable to you.
What happens when you jump into something new is that you just repeat the same patterns. The other person is new, but your history isn’t.
I did not learn any of this until I was mid 40’s, and finally the penny dropped. Met someone great and I had really understood why things hadn’t worked before.
You often meet people - in your case your ex - where they just repeat the same stuff. They go from relationship to the next one with no gap, but really the person they meet isn’t even that important. It’s just the new, next person.

It's different for everyone. Don't pressure yourself to conform. Take your time and see where life takes you.

Do you think counseling would help? Talking about yourself to a professional could reveal what would benefit you.

I don’t think he has come out on top
its not a competition
he's still a crappy person
hard as it is, dont think about him - what does you life look like now and what can it? Plan something for yourself that will make you feel good and repeat that 💐

Because he’s a thoughtless prick who cares only about himself?
he’s not even grieved your relationship - well he has and was probably planning his exit long before he did so he’d made peace with it
its cruel and reflects badly only on him
a year is nothing - focus on you, what you want from a future relationship and invest in yourself