The advice you've had to find a solicitor is good advice, I second that.
On a slightly different slant... you've had years of being old what you can't do/ aren't good at, let me put your value to you in another way. How many of these can you do? (I expect all)...
Speak english; read; write; post a letter; add, subract, divide and multiply with a calculator (even if you work slowly); fill in a form (even if you have to phone to check what 1 or 2 of the questions mean); make a telephone call; answer a telephone call; turn up on time to a pre-agreed meeting (when there are no emergency changes in circumstances); ask a question when you are not sure about something.
Honestly that is the sum total of all the skills you need to run the paperwork side of a household.
It helps if you can also...
Use the internet; write an email; read an email; send a text message; read a text message; print out a document on a computer.
None of the above are essential though.
When you take the confidence crisis out of it, you're clearly literate, if you can use a computer to talk to us you can use a calculator, I can't imagine the phone or meetings being a problem- you will have had plenty of practice with keeping in touch with the childrens schools over the years.
You can run a home. All you need is someone to tell you where to start. The solicitor will help with the big things like helping you understand any rights and responsibilities in a split and we can help with the small things like telling you how to change an electricity supplier or if you should apply for a benefit.
As you're not married then I think your solicitor is going to say that you and the children need to move out, but even that is less daunting than you think. We can talk you through it if you like, the only silly question is an unanswered one.
One more thing, if there is any hint of domestic violence, if he has ever so much as slapped you, then I think you should mention it to the solicitor.
Free advice from fully qualified solicitors is available to women in your position through Rights Of Women so that might be the best place to start. They know thier stuff and I'm sure if you explain what you told us about never having had any responsibility for paperwork matters that they will explain everything really thoroughly.
You can do this y'know. We're behind you all the way.