It sounds so tough for you at the moment - but it will get better, I promise.
Mine was living with his wife despite telling me they had separated and she had met someone else. Even showed me the divorce petition (which he had made himself from a template on the internet)
I thought I’d never get over it, would never stop crying and never be happy. But I did, and I am.
It took a solid 18 months, constantly going over in my head why he did it, why me. But you know what, who cares why. I have my own life to live.
He contacted me through a friend over 2 years later. I wasn’t in the slightest bit interested in hearing why he did what he did. I didn’t care.
And neither will you, in time. You will be almost grateful for the lessons you have learnt, once you see yourself get over something like this, you realise how strong you are and that you won’t stand for anything other than total respect and decency from here on in.
Be kind to yourself, you took the leap and it didn’t work out. But you survived before him, and you’ll survive after. What really helped me was thinking back to a time when I was younger that I had a problem and thought it was insurmountable - and then realising I had got over that and how insignificant it now is.
The sun will rise again, and with it, you will grow stronger, move forward and find happiness, be that alone or with a new partner. You just have to hang on in there - he is a shit person but that’s on him - you are not.