I’m so sorry OP. I just wanted to hold your hand.
This is REALLY hard. It’s really hard, it’s really painful it bloody sucks.
It is not your fault.
I’m afraid you need to reframe the way you are thinking about your ex and his actions.
You we’re NOT “both very much wanting to make things right” - he was more interested in shagging another woman.
He is not staying with her because it is “the right thing” - he is doing it because that is what he has chosen (and he is hardly doing “the right thing” by talking to you about it in this way - it’s not what he is telling her!)
It is not ok to behave like this “because of a rough patch” - that excuses nothing and twists his behaviour onto you in a completely unfair way.
Likewise saying he still loves you, hinting about the future etc is just a way for him to try and have his cake and eat it.
OP. You are NOT cake!!
Try to manage the mornings and give your kids hugs. Then give yourself permission to cry all day if you want while they are at school. Likewise once they have gone to bed. It’s ok to tell them you’re sad, but try to reassure them that you’ll be ok. Feeling sad isn’t shameful.
See the GP as a priority.
Write down a few things you need to do and whenever you have the tiniest spurt of energy try and tick one off. You say you’re struggling financially - it would be a good idea to try and speak to a solicitor about what plans could be put in place regarding your home and financial support etc. That might be too much right now but it needs to be done soon.
Try to reach out to a close friend or family member for some support if you can. When you get out of the house at the moment where do you go?
Most of all, try not to interact with your ex even if you just set yourself a target of a week, or two or four initially. Try to focus on yourself - feel your feelings, talk to people and allow yourself to look at this man’s behaviour towards you as it really is.
Please don’t worry about your children loving him more or having more fun with him. Maybe they do have fun with him right now - it doesn’t matter. You are their safe place and their mother. They need you and they love you more than anything in the world. You’re going to be ok - and they are going to see you be ok, and know that people can recover from grief and pain and all the shit the world throws at us. Try to stay in the NOW. And take one day at a time.
There are lots of people on this site who care about what’s happening to you - you are not alone.