Oh Poppy - bless you. It's OK to feel crap right now - honestly. Of course, you are mourning the good bits. We all do that. It's normal. But don't kid yourself - it was not all roses, otherwise you would not have felt what you have felt and for a long time, by the sounds of it.
As I see things - he has a fantasy view of what our relationship, and what our home should be like. The reality of life with me and my son does not fit this - hence he's off. He says it's because living with us is unbearable. I think he's off to start hunting for a new partner, before he's too old.
My Ex-DP is exactly the same. Wanted the fantasy. Actively spoke of wanting perfection. Well, life just ain't like that.
And - shock, horror - not everyone in every family loves each other dearly and gets on fine all the time.
Family niggles, strife and conflict happens to the best of us from time to time - it's how a person handles it that matters. Do they a) feel hugely aggrieved that their perfect world has been tarnished, have a fit, blame their loved one for everything that's wrong, storm off / threaten to change the locks / actually change the locks/ go silent for days etc etc etc?
Or do they b) grit their teeth, swear quietly under their breath, get on with it, speak frankly but respectfully and get it out of their system, have a good yell / cry, put a brave face on it, make compromises for the sake of the person they love the most, see the funny side, get stuck in, actually value the relationships despite all the ups and downs?
I wanted to find option B in my Ex-DP. I looked for it, craved it, tried to nurture it. But whatever I did, it just wasn't there - it took me a while to work it out, but no matter what I did to try to change things, I was looking for something in him that I would never find.
IMHO you Ex-DP is totally unworthy of you. So what if he's off to find another woman? Poor woman is all I can say. He should have a health warning tattooed on his forehead.
I had counselling this morning - in floods of tears for most of it - and for the first time in my life, it was suggested to me that the roots of my issues lie in low self esteem, probably from childhood. It is a revelation and I'm now on the latest stage in my journey. I wonder perhaps whether you too might have similar issues? I am a few weeks further down the line from where you are at now - and like you I loved my Ex-DP so much that I put up with no end of abuse, because I loved him. Now, even just a few weeks later, I look back and think - hang on - how dare he have treated me like that?
BTW - most people who know me (not well, though) would be stunned at this suggestion as outwardly I am the epitome of confidence and career success. But inside - until very recently, I honestly didn't know who - fundamentally - I was, beyond being a (hopefully half decent, mother, daughter and worker).