You have to wash the mud off to borrow the analogy from The Life Boat post (copy and paste into address bar):
You know drinking and smoking aren't helping you but you're doing it anyway. There's a lot of self-pity in your words. Calling yourself useless for example.
I too have had years when BW and I weren't emotionally present for each other.
You say you don't know how to get your shit together, but are you sure you don't know how?
Or is it more that you just don't want to because you think you deserve to feel horrible and awful.
My advice, after you go read "The lifeboat" again, is to take baby steps. Feel awful if you must, but if you're not eating, then drink some meal replacement shakes like Ensure. Not taking care of yourself just serves to make you feel worse.
You feel like you deserve to feel worse so you stop eating. Well, eat anyway. Set an alarm to remind yourself to eat if necessary. Take vitamins. Meditation music and melatonin might help with the sleeping.
Feel a bit better, act a bit better.
You're not alone. Nightmares are normal. Feeling overwhelmed is normal. Having bad horrible days is normal.
As long as you still have your BH and your kids, you have a gift: the opportunity to make things better. Spend time with them. Make up for those years. Learn about them. Hug and kiss them.
I couldn't stop myself from crying in front of my son. Like you, seeing him made me cry even more because I realized some of the same things. He would try to cheer me up; my 10 year old.. That would make me feel even worse. And then I got some 2x4's (constructive virtual smacks to the head) from folks here telling me to suck it up and that no 10 year old is equipped to handle any of this.
And... it got better. My relationship with him has never been better. I'm learning to listen to him and repeat back to him and "letting him exhale" about his issues.
Maybe it's common sense to some, but for me I needed a little help with my listening and empathy. I would like to suggest to you the book "Just Listen", you can find it on Amazon, if you want any support in that area. When you make it about them, and not about you, you're taking the first steps of not being selfish.
You don't get past this. Ever. You learn to live with it and grow from it. You'll never see the world the same again, and that's OK.
Keep your chin up. One foot in front of the other. One day at a time. You can do it. Go be the wife and mom you want to be.
Keep posting your thoughts here. Even if you don't actually hit post. The mere act of writing/typing can be healing in itself.
(edited for typos)