Hi L.!
Trust me...ending the marriage should be your very, very, very last resort after every single avenue of rekindling your relationship has been exhausted. You will regret it if you don't at least try to make it work. I regret my divorce.
First, I don't understand how your four-year old thinks its your fault. How old are the other siblings? Is he being "told" by someone else that it's your fault? How do the other children feel? If that is the case, these children are being fed some real bad info from someone. Usually the mommies are the caregiver, the loving and comfort person that the children see and not a person at "fault".
Anyway, going on what little bit you gave, my suggestion is to find a babysitter for an evening and you and your hubby go on a date. It's a start. Remember and talk about what attracted you two to eachother and talk about how you got to where you are today. Count your blessings. Know that the two of you made a commitment to eachother, your families, and GOD. Once you think you and your hubby are both feeling relaxed and are on the same wave length, then start talking about what has been the problem with the marriage lately. Use the "I and me" approach. The minute you say "you", he will feel targeted and will automatically put up a defense. For example, don't say, "You are always late getting home from work." Say something more like, "Is there something at work that is keeping you from being able to leave at normal quitting time?"
And say things that start out "I feel unappreciated when..." or "It makes me feel bad when..." Don't put him down in any way. Men need to feel strong, even when they know things are falling apart. So don't make him feel he is weak. Let him know you are his partner for life and that the two of you are in this together. Take a good look at yourself and maybe point out a couple of things you may be willing to do or change to better your relationship. Tell him these things so that it doesn't look like he's the only one who has to make changes. Also, let him talk!!! Even if you are in the middle of making a point, stop. Especially if he is a person who has a hard time opening up (most men are).
Boy, I could go on and on. I've been divorced for 5 1/2 years and am just now feeling like I can put that behind me and move on. Even though I am already married and have two more children, I still struggle with this regret daily. It's getting easier as time goes by. But I feel if in my lifetime, I can stop one marriage from breaking up, then I know that something good has come out of this.
Best of luck to you and your family. Please keep in touch!
AMH :)