I know crying is fine but I just don't want to let go completly because I don't know if I will stop.
Oh Nic, I totally empathise on that one. My advice, FWIW, is to literally pick a time when you CAN break down (ie when all the children are safe and alseep) and just allow yourself to have the most massive cry. Let it all out.....a huge box of tissues for all the snot and some loving arms to fall into helps........

It will stop (might take minutes, probably hours) but when it does, you may feel a slight sense of relief?(You'll most likely feel utterly exhausted......)

Hugs to you.

And certainly from what you have said about Isaac and the cat.......I totally agree that it was not about the cat as such. (When my Dad died, about 10 days afterwards, I spilled some hot tea on myself. I remember crying the hosue down over "my burnt hand".....and throwing the tea cup to the floor......it was all just an excuse to get the rage and pain & frustration and tears out....)

Take care of yoruself babe........