To feel so hurt

He is an arse, frankly. He couldn’t be bothered to be a dad before and now he’s performing the role of dad to get this exact response. If he cared about the kids he would respect your boundaries and he would have behaved like this perfect father at the first time of asking! My ex used to hang around with tears in his eyes (I kid you not) so that our then 2yo would protest that she didn’t want him to go. He would FaceTime us and tell her he missed her, which upset her.

When we lived together, he couldn’t be bothered to bath her or play with her, he was too busy heading out the door to see his “friend” and help bath her baby (still not kidding).

It all sounds rather childish and petty from both sides.

you said he wasn’t supportive and you resented him so why would you be bothered if he’s found someone else. Be happy he’s now someone else’s problem and not yours.

focus on your children’s wellbeing and stop kicking out and then inviting their dad back into your home every 5 minutes.

if he wasn’t a good partner or dad you’re not missing anything with him gone.

He's talking about her on purpose. Because last time he did that you begged him to come back. If it makes you feel any better, he may be with someone else, but you could have him back again if you chose. Is that what you want? You've tried twice and it hadn't worked. Do you want to try a third time? Or do you know this isn't going to work and you need to stick to your guns? You're going to have to decide pretty quickly. Because at the moment it looks like he'd still rather be with you. But things change and this might not continue to be the case. So, do you want him, with all his faults and issues, or are you going to let go and properly move on?

How old are you both? 17?

Can you play with them before bed? Weekends? What did you do when you were together but he was out working and socialising all the time, did you have time to play with them then?

Why doesn't he make their tea at his place on his days?

This will give you a chance to have time to yourself, or catch up on chores or do some batch cooking so you have more time to play with them when they're home.

This is very wrong and unfair to everyone

He is being hurtful but you left him. Twice.

You don't want him. You let him go.

Be grateful he isn't in your life anymore. Spiteful prick.

They only miss him since he's paying them attention, which he never did before.

He's trying to make you jealous regarding his new woman.

Don't fall in to the guilt trap regarding your children.

He’s playing you like a fiddle OP.
Disengage.
Don’t let him use the kids like this.
He wants you to get jealous like before, so he’s talking about her, to goad you.
Just be indifferent. Grey rock him.
It takes two to tango, don’t partake in his stupid games.

They're young, they won't understand yet, but it is important to ensure your dcs grow up seeing kind and decent relationships.

@Joolz20 You don't want to be with him but don't want him to be with someone else?

Sorry, but YABU! This "man" is a man child and wants you to be his mum rather than his partner and equal and is never going to respect you. You know full well you're better off without him so there is absolutely no point feeling hurt because quite frankly you should be feeling sorry for this other woman who will now have to put up with a man child once the initial charm wears off!

He's a nasty selfish, manipulative creep. You leaving him doesn't change that. He thinks he can string you along, to hurt you.

Well done for leaving him. Ignore his small minded meanness and be proud that your children will not grow up seeing him treat you like that.

I suspect he hasn't got another partner at all and is trying to wheedle his way back into your affections OP.
Don't fall for it.
Stop speaking to him about anything other than essential need to know stuff about your children.

Disengage!! Grey rock - he is trying to get a reaction from you, don't let him.

He is your children's father, that is all he is to you and the only relationship he needs to have with you. Shut down any communication about anything else.

God OP he sounds truly pathetic, please try and ride this out to make it to the other side! Once there you'll look back and be astounded that this loser ever had any control over you. I 100% second every word of advice from @MatildaTheCat

YANBU to feel hurt but YABU to dwell on it and let it take up any more of your time.

Have you ever heard the saying 'let them'?

Let him go and do what he likes, it makes no odds to you unless it interferes with planned contact and if it does, cool, that's his choice. You can do more fun stuff with the kids.

As we said previously, it isn't because he is comfortable doing it. He wants to hurt you.

Let him drop them to the door
Tell them - let's say bye to Daddy, see you soon.
Close door and get on with life.

If he tries to engage you with any comments:
Blank face/ expression
'Oh really, ok' or 'oh, ok. That's nice' EVERY SINGLE TIME he says something about another woman.
Ignore if he asks about flowers
I've got to go and sort the kids out now, see you next time
Close door, get on with life, give him no more headspace