Ypu have no control over him and what he does. But you can control yourself.
To a degree, it is a choice to spend 5 months crying every day.
You have to choose differently and that is how you get over it and move on.
When you find yourself sitting and thinking about him, find something else to do. Don't let yourself dwell on thoughts of him, her, or fairness. Give yourself a talking to - come on! What are you wasting time crying over him again for. And stop. The crying that comes from an initial shock can't be helped but the sort of crying that is happening 5 months on has become a bit of an unhealthy habit and you might find that if you tell yourself to stop, you can.
Tell yourself (out loud if necessary) that he doesn't deserve your tears, you've had a lucky escape because you deserve better than someone like him, think of things you can do now - eg decorate the house how you like, eat what you want, watch what you want without having to consider him. When he takes the children away, rather than dwelling on the fact she wil be there and thinking about it, plan some things you can do for yourself whole they're away. You need to make the choice to take your life back and move on. It won't just happen if you are stuck in this cycle.
I'm not being flippant but what you are doing currently means that, 5 months on, you are still crying every day. Choose differently.
You need to find your strength or, rather than getting to the 12 month mark and realising how much better your life is, how much you've achieved, you'll still be sitting there crying.
Ypu can do it. Many have before you and many will after you. You just have to choose to do it.