I didn't want to read and run 💐
I have an idea about how you feel, like you know you won't do anything in itself (the idea that you'll just mess that up too is your minds way of telling you that you know that's not the answer) but the idea of just disappearing off the face of the planet can be so appealing.
It's always easy for others to tell you it will get better (and it will, one day) but that doesn't help as right now you probably can't see how that will be.
A lot of what you say about why you feel you shouldn't be here are symptoms of your circumstances and not a "defect" of you. Flying off the handle at your children show you are under pressure without some where you feel you can turn and are certainly not an indication that your children would be better off without you.
I'd love to have some magic words that would help you see your worth but I also know that you probably wouldn't believe them just now.
Sometimes it's better to stop looking at the bigger picture and just look at the tiny little things, be that the small pleasures you have with your children, a little smile or giggle, a silly comment they have made without knowing what they were saying. But also look at the things that are bad in tiny pieces too. That way instead of being overwhelmed at the thought of trying to change what is wrong all at once just focus on one tiny thing at a time.
What is the one thing you would like to change the most? Then break that down into smaller bits and try and do one thing to change that.
You've already made one step, you say you have nobody to talk to but you've reached out on here so that is a massive step forward.
We may all be strangers on the internet but that doesn't mean to say you have to go through things on your own.