How to deal with intrusive thoughts/night terrors?

ever since I became a mum 3 years ago, my brain has betrayed me.

when im relaxing, trying to sleep, or even when I finally *do* get some sleep, all I can think about are situations in which my kids are in danger and I can't help them.

I wake up in sweats and sometimes crying, and have to check on them to make sure they're ok.

Quite often I have insomnia since I dont want to relax or fall asleep because the thoughts are terrifying and really troubling.

my partner does not understand, and just tells me to "shut it off".

does anyone else deal with this? do I need to seek help, or is this normal?