LW - I know how sad and rough this is for you, but in all honesty, I wonder how many things you have coped with alone, even though you had H in the house. You coped with all the early stuff about ds1's school issues, concealing things from h for fear of his reaction, you have dealt with so many big important things in secret, or in an emotional sense, all by yourself. I'm not at all trying to make light of everything you feel about this break up, but in so many ways, you have already been alone. Even when you were a child.
You will grwo stronger in time, and even though things are hard and gnaw at you, I think that once you get this horrible process over, little chinks of happines might break through sooner than you think.
No-ones expecting you to bounce back going 'hi, folks, let's party' in the near future, but whatever the future does bring, it won't be all bad.
you are clever, beautiful, well-respected at work, and have a great relattionship with your boys. Somewhere, sometime, when your guard is down, you will find you are unexpectedly happy.
And you so badly deserve it.