Hello - another one here whose husband just upsticks one day, no notice, no warning, after 15 years together. Now 5 and a half months later, I'm in the thick of a divorce (acrimonious one). I felt horrified by the idea, humiliated and hurt.
I took around 3 months to stop feeling total and utter despair, I mean the 'I just want to die please' feeling. So please, please, please forgive yourself for feeling so dreadful. It's also okay to be bloody angry at the world and at her too, but mostly at him.
As others say, get out and about as much as you can. Nothing destroys your self-esteem as much as your husband walking out on you, but by getting out and about, you'll find your self-esteem grows.
Also having to do tasks, perhaps, that were 'his job' as helpless and useless as you feel, once you've faced them, will make you feel a sense of accomplishment. For me it was learning to drive a car (again) but it could be anything at all. Also don't be afraid to ask for help - most people in this world are generous and kind, and will help if you ask for it.
As best you can, don't turn on yourself. It's too easy to blame your saggy boobs/large arse/big nose (or whatever your 'ism' is) for him leaving. He left because he is selfish. He also left you with all the responsibility. That makes him a coward.
Don't believe a word of what he says. It's all bullshit. That includes anything he says about what he is going to give you in divorce. On that point, see a solicitor (in fact several) - things may not be as bad as the media leads you to believe (although it's bloody hard until you get to the settlement stage).
And yes, to the "No Contact" rule (and try not to do Internet Stalking as it'll just make you feel worse). Any contact you get from him is likely to be either a) nasty or b) heartless. Don't be surprised if he never, ever again asks 'how you are'. They don't like guilt, and they don't like to be guilted. So ignore them no matter what they say.
I know it sounds daft, but just re-organising your home (giving it a paint, or rearranging the furniture) does actually help. He's left the home now, so it's not his. Do whatever you like with it. Remind yourself: The day he left was the last time he gets to make a unilateral decision over your life. You're in charge now.
It takes a long time to adjust so do not let anyone tell you to 'get over it' (mother!) after a couple of months. See a doctor to get signed off work if you feel that is necessary for you, and also to get some anti-depressants if you think they will help.
At the moment, counselling is probably too soon, but don't rule it out in a couple of months.
And finally, cry your bloody heart out. And don't stop crying until your tears dry up naturally. It is get through each moment as it comes for the first few weeks but you will start to feel more human again in a few months (promise).
I firmly believe: "His decision to divorce devastates me, and relieves him. The act of divorce will relieve me and devastate him". So far, so good.
One day, you're going to be amazing if you choose to be. He will still be a selfish coward and twat, but will end up the bitter one about his divorce.
Some reading that I found helpful:
Runaway Husbands
Detach and Survive.
Take care. Sorry this has happened to you too.