I'm not actually sure that antidepressants that make you feel.even worse for a couple of weeks are a great idea in this situation.
You might feel better after a bit of time without feeling even worse and having anxiety due to medication now. I don't know.
Look.you want to tell him you're in pain probably because a. You think he might come back and that'll relieve the pain or b. He'll know you still feel.the same way and aren't getting over him/moving on/still care deeply etc.
But the fact is that, he's known you're in pain for a week or two and it didn't cause him to come back, and he knows how you feel and he hasn't come back
It won't change anything.
He'll come back if and when he feels like it, when it suits him.
Fwiw I think he thinks (correctly at this time) that he always always has the option of going back to you. That you will always take him back. No matter what. You are there as a permant fall back. So he has no urgency whatsoever in going back to you. And whether he does depends on other things that you gave no.control over (does he feel like staying single for quite a long time, does he have other people to fulfil his needs (home comforts, sex etc)., does he get into another "relationship" in which he gets challenged even less than in yours to act decently (that's perfectly possible given it would be a much more casual relationship without a child and without living with them).
Do you may think "how can he do this to me" - well, he sounds like a right *nt to begin with. And he sounds like his commitment level in relationships is very low. And also he thinks he can go back to you any time he feels like it in the future. He has no loss to process - because he believes that (correctly at time).
The thing is is this type of guy even truly bothered by loss of that type? He sounds v hard headed, selfish, laddy, disrespectful, and cavalier. You won't change that. He doesn't sound cut out for a real relationship or family life. He'll probably just flit between baby mamas.
It's very hard but if it helps you need to tell yourself that you're split, though it's not impossible you'll get back together in the future; but that wouldn't actually be a good thing for you even if you did. Allow yourself the out from thinking about the split and him. You have to limit it, you can't wallow or you'll go mad.
You need to fill you and your kids day with stuff and have plenty of things to focus on and distract you. Try new things - sports, hobbies, anything with the kids. Try things that force you to concentrate on them.tk.learj them and it will stop you thinking about it for those periods, it'll break the habit of repetitiive/compulsive thinking about it.