Am I the being unreasonable?

[BeanEm]

Just a little bit of background, my son was born 12 weeks premature and it's been a ride! My MIL can be quite overbearing but is our extra childcare for evenings/non nursery days/ last minute work changes. Which has been absolutely life saving and fantastic!
We live in a top floor flat with no life, I appreciate it's not ideal for everyone, but she knew this when she told us she didn't want strangers looking after him and she would do it.
However, for the attempted 2nd time now, she has said it will be easier for everyone to have him stay the night at theirs because me and my partner are working. (The last time I was poorly and she was being really nice but I literally burst into ugly sobs as this had been taken out of my hands and she decided it was best for everyone)
So I've just ended up having to take the shift off work so I can have him at home and see him in the morning before I go to work again.

My partner thinks I'm being ridiculous getting so angry and upset about him 'just spending the night'. It doesn't feel like its just the night to me. It feels like she is another person who is trying to control my time with my son.
This stems from the NICU where, during lockdown, they limited visits etc to keep everyone safe. But I had no say in my child's care or routine or anything and felt very out of control and it was a really tough time. For which I'm about to start counselling for.
It just feels like I'm losing control again and no one is stopping to make sure I'm happy with the arrangements.

So, am I being unreasonable? Have i explained myself properly??

Have you discussed with your mil about the issues with you feeling a lack of control over things due to your son being in nicu when he was a baby? it seems to be that alot of this stems from that and the fact that your mil agreed to all this, insisted on no pay childcare but is now changing plans last min.
but she might also be genuinely confused about why its ok for your son to stay sometimes and not others, and missing the fact that its the lack of planning etc thats the issue.
you dont have to go into the whole situation with your feelings on the nicu situation, but theres a chance you have a bit of ptsd from it and i think things would be a bit easier if she had a proper understanding on where this all stems from

@NuffSaidSam

I think it's going to be a lot harder to find reliable, consistent, good quality childcare for those hours than you think.

It's unlikely to be a case of 'well we'll just get a childminder then'.

Maybe you need to change your thinking around this, rather than hers. So just accept that on a night that she has him, SHE chooses where he sleeps (whatever is most convenient for her). Every single other night of his life YOU choose. That way it is in your control because you are CHOOSING to allow her a say on the nights she has him. The other choice is using paid childcare who I guarantee won't love him like she does. It's your choice.

This is great advice.

Can you look at it as her relieving you of some of the mental load?

To add my overnight charge from 6am to 7 am would be £100.