Chris06, sorry to hear your situation. It is a very tough thing to go through. It has been the toughest thing I ever went through, and I'm not totally out of the bush yet. But it does get better with time. Your most important tool is Patience and Faith if you believe in God.
The toughest thing is when you try to use logic and tell her that you will fix things, you didn't know she was unhappy and you will change, but you get a cold response and she says something like "it's too late" or "I don't love you anymore". That's tough to swallow because us men are used to analyzing and fixing things. We want to be in control. When something is wrong, we want to understand it and fix it.
Also, every situation is different. I see some positives in your situation compared to myself and many other people here, but I could be totally wrong. First, your kids are still young which could play in your favor. Also, you know exactly what you did wrong: you were not paying attention to her, you worked away from home, etc. And she told you in the past exactly what you needed to do. So that's a good starting point. You know the things you need to fix in yourself. But you need to do them for you and not for her.
One of the concepts that I always struggled with, but you should embrace is what makes you attractive and what makes you unattractive to her. I know it's weird because you have known each other for so long, but that's how it is now. You need to accept it. You need to treat her as a stranger because she looks at you as a stranger (don't ask why. It makes no sense.).
And so you need to stop doing the things that make you unattractive. These include begging, being needy, weak... And you need to start doing the things that make you attractive, like showing confidence, being independent, strong, etc.
You should do a 180, meaning, in my understanding, you should change your bad behaviors totally. I also wouldn't recommend doing things to help her, just the bare minimum but don't get out of your way for her.
But be kind and gentle all the time. Don't do anything impulsive that you will regret later on.
Don't say things like I love you. Not the right time. Focus on yourself and let things take their time. I truly believe that your situation is not as bad as others, but I could be wrong. You need to give her time.
If she decides to come back or if shows interest, stay cool but gentle. Don't expect too much. She will not change all of a sudden. If she does, you will need to move slowly and understand that she could send you mixed messages all the time.
Understanding why is not important. Maybe she is confused. Maybe she has a plan. Who knows? You must learn that it doesn't matter. You have to do what you have to do regardless.
Me:49 XW:41, M:18 years, Kids: S18,S14 BD:JULY 2017, W moved out: DEC 2017 Filed for D: APR 2019, D Final: JULY 2019