Sister, I wish there were some magic to help you right now, but while there’s one it’s inside your self, I can’t "cast the spell " for you.
You can though.
Breathe first of all, from the belly and think one thing. What’s scaring you right now?
Is that he is going to leave or that you took back an unremorseful cheater thus "wasting your time "?
If he does not change and hasn’t changed, you are actually gaining from "losing" this person.
That’s a life vampire an emotional parasite, you have done nothing wrong to him and he did the worst to you.
You might be used to him right now just because he is familiar like a intestinal worm, and you invested in what you believed was a relationship while he was siphoning off all the nourishment he could and gave you an infection of the soul in exchange.
You did nothing wrong, not to him, you sacrificed enough of your good to feed his emptiness and insatiable void.
Getting him out of your system is going to be the best thing that happened in your life.
I know you are experiencing grief and that feels like chaos, but he is the source of it, not the thing preventing you from falling, he is the one who is throwing you under the bridge.
Your nerve system feeling initially relief is what you truly feel emotionally, because you know he never wanted to change. the rest is an aftershock but it will pass, and you’ll find yourself again