Baby Daddy has a new girlfriend,am I being irrational?

So, my son's father has a new girlfriend, let's just call her K (well, they are seeing eachother...) they aren't official. I don't care about that. But he hardly knows her, and he hasn't seen his son in 4 weeks due to 'being busy'.

He came and grabbed our son tonight and only told me on the way down if he could take our son to stay at this girls house for the night. I was reluctant but said yes anyway, that's fine. She's a childcare worker.

And something he said really pissed me off.

At first he says "she knows more about children then most mother's do.." mind you this girl is 22 😒 I thought, yeah well she doesn't know about MY child, and every child is different. Just because you're a child care worker, loves kids and grew up looking after you brother and sisters doesn't mean you know everything about children as all children are different. I don't know why it annoyed me so much?

He came and picked him up and I told him that our son hasn't had the dummy for 4-5 days as i've lost them all 😂 (mum life). Our son ONLY has his dummy for sleep, never any other time. Our son is 21 months, so will be 2 years old shortly, and he turns to me and goes "Oh well K said he shouldn't be having the dummy anyway, because he'll get buck teeth..." I just stared at him and rolled my eyes, and told him "yeah, i've already told you that before, but he only has it for sleep and doesn't have it in his mouth 24/7 so he won't get buck teeth and he won't be having it past 3 years old anyway."

So now, she's trying to tell him all these things he should be doing with his own son 😳

And I'm laying here in bed stressing out thinking she's doing to try and dictate my parenting and TRY and tell me how to do things. Seriously she better not, or I'll be pissed 😂 I won't get fully mad at her if she does I'll just be like, look girl if you want to parent someone's child, have your own. I'd love my son to have a brother or a sister, but I'M his mother, you can't come in here changing shit because you think you know better because you work with children and infants. I sound so petty right now. Ew. But I can't stop thinking about it.

Just a quick edit: I have absolutely nothing against him dating because I date too. But I never let the men even talk to my son unless we become official (which obviously hasn't happened yet because I'm still single), I'm just paranoid about it. Like I don't want every guy meeting my son when we aren't going to be official? I'm also really happy he's found someone and that he's happy but I'm just worried about someone trying to mother my kid when she hardly knows him. And him thinking that because she's a child care worker, she knows more than me? Idk. I'm just worried. Other than that, I can't wait to meet her and whatever I mean, IF she's going to be part of my sons life. Apparently she wants to meet me too? I just don't want her trying to do anything related to my child. Like she can play with him and feed him and things but like not actually parent? He's in my care %80 of the time. So I don't want her ruining his routine because she thinks she knows more about children and how they 'work' I guess? Or try and get him to change my mind about how I am with his routine? If that makes sense. And I'm worried she's going to pick on things about his routine of how I do things with him like the dummy thing when it isn't even her place to say? Like I'm worried she'll judge me or something 😳 why the fuck am I so worried about a random woman judging me? Maybe it's because she's a child care worker, I just don't want her picking on me for little things.

EDIT: thankyou for all the comments, I like constructive criticism 😂 I've thought about to alot since yesterday and I'm overthinking and being super irrational. I need to trust my ex's judgement and trust the woman he's seeing will look after my son and not try and take over, I need to see what she says as her just helping and giving me advice instead of judgement (because of course my mind goes straight to that) 😂 I'm a hardcore overthinker and I need to snap out of it. Stop feeling threatened by her when there's no need to, I'm his mother, nothing she does or says will change that. She can say as much as she likes about how children are and give me advice, I don't NEED to feel threatened by it or feel like I know less or more than her 🤦 it's my choice weather I take it on board or not. I mean, I'm grateful that my ex has found some that's great with children and she's not a drug addict or a toxic person. So I think we'll get along really well.