OK, that's clearer now, thanks.
Do you want to be in the relationship? I think that might be the first thing to work out. I would forget the CBT for now, unless you want to use it to help you to work through that (not sure if it's helpful for that kind of thing?)
I really doubt you are being toxic to your girls. It's one thing to be more on edge or emotional, and another thing entirely to be manipulative and cruel. It's not great to be shouty but it's not the end of the world - and working on yourself and your situation ought to improve this, too. Perhaps you could ask your CBT practitioner to help you redirect when you want to shout/lose it at the children, how to deal with it more productively and calm down so you can deal with the situation in a more effective way. But do look at the relationship stuff as well, though it's painful I imagine.
There are two organisations - Rape Crisis, who have a phone line and various centres around the UK - look at your nearest town/city on that list. And then there is Women's Aid, who specialise in partner abuse. (It doesn't matter if it was a one off or whether there are ongoing issues or even if there are both but you see them as unrelated.) They won't push you to leave if you don't want to, but they can advise you with help and support to try and work out your own feelings, basically. They also might be able to advise about a local specialised counselling service, as it comes under the umbrella of domestic abuse.
Even just a once off incident occurring in adulthood can lead to situations such as PTSD, panic attacks and generalised anxiety - especially if at the time as a coping mechanism you minimised or convinced yourself that nothing wrong happened. This is really normal and you shouldn't be ashamed or feel silly about it - it's a coping mechanism where your brain basically tries to minimise the harm caused to you. Unfortunately while that might have been extremely useful in caveman times to allow the panic not to set in immediately, which could have been life threatening, it doesn't work so well in modern times, we do need to deal with things eventually.