I'm 6yrs ahead of you on this. XH flounced in the January (because I'd dared to pull him up on his drinking, after yet another "I promise I'll engage in rehab/abstinence" lie). He'd flounced/gone AWOL before, so I wasn't AS upset at that point. I thought that living apart for a time would give him the chance to really work on stopping alcohol/drugs and work on our marriage (that was what he told me as well, when he got in touch with me afterwards). I did put in strong boundaries about what I would and wouldn't put up with (I should have done that years before!!). 8 weeks later, he dumped me. I then found out that there was a OW (actually one of my now ex friends) that had been on the scene for months, and he had moved in with her. He told me that she was way better than I ever could be etc.
I cried and begged too, when he ended things properly with me (probably trauma bonding). I think because I couldn't believe that he was so quick to end things when I had done so much for him. Honestly though, he did me the biggest favour: having to deal with his antics was horrific; both the DC and myself were suffering (even though I tried to shield the kids as much as possible). DCs' behaviour and school grades both improved in the short few weeks between the day he flounced and the day he dumped me. The house was more peaceful and orderly. I slept better.
When he properly ended things, I felt sick, scared and couldn't eat much. So, I took things an hour/day at a time. Forced a smile on my face when with the kids, and when working etc; told my friends, colleagues and family so that I could get support; made sure I said yes to any social invite that I could make etc; made sure I was on top of things in the house. I think that - and keeping a good routine with the DC/life - helped. I did a lot of practical things too - spoke to a solicitor, boxed up all his crap, decluttered etc. It helped to take my mind of all the shit.
Time is the thing that helps though. Give yourself time, be kind to yourself. You're grieving a loss of sorts, a huge change, and that takes time to deal with. None of us go into a marriage or relationship without thinking it would last our lifetimes. I certainly didn't, and I meant every word of the vows I said in front of my priest, XH, family and friends. All of us want a happy ending and a happy life.
I tried to remember the shit things (luckily there were many!) and how I now wouldn't have to deal with that shit. About 4/5 months later, XH and OW split - all very dramatic and they both came crying to me about it (I shit you not). I told them both to GTF and told OW that she could keep him, and that he wasn't my problem anymore. He begged me to reconsider divorcing him (by this point, I was flavour of the month again) and for us to make a go of things again, but divorce papers had been sent and I wasn't prepared to stop any of it.
I hope you managed to catch some sleep. Try having something tiny to eat/drink. Self care is so important. Sending you lots of love and strength x