I am 11 years on from an out of the blue announcement after 10 years together after XH met "she's just a friend". I understand how you feel. I was in a state of shock and grief for a long time afterwards.
It doesn't consume me any more but it did for several years afterwards and I had a lot of counselling to come to terms with it all. A PP mentioned PTSD and it is very like that, reliving it over and over, trapped in circular thinking ,if only, what if, and reliving moments over and over and so on and so on. I deeply mourned the loss of our family and our future together that I thought we would have. I had been on my own for a while before meeting XH and when I met him I fell hard and it seemed that he did too and he seemed so kind and loving and a decent man, that I just really thought that was it for ever and ever, so the loss hit me very hard.
Counselling was the only thing that helped me and I had a lot of it over 2-3 years before I could finally let go of the hurt and the dreams and move on. I have let go of most of it, although there is still a small part of me that is hurt, it's boxed away now and I don't let it out very often.
I didn't want to carry the hurt with me for the rest of my life , I had to let it go.
I do not communicate with XH on any level at all now. He is married to the "she's just a friend" and has a patchy relationship with DD as he moved away and doesn't see her very often.
You will move on and I recommend counselling even if you have had some already , pyschotherapy really helped me in the end as she helped me to view everything from a different angle, helping me to face up to reality and look to the future.
It has changed me forever though, I will never be the person that I was before, I lost the happy go lucky me and that still makes me want to cry even now.