Everyone on here thinks "Gosh, she knows someone who has been through everything." To a certain extent that's true but I like to use examples.
My mom met my dad when she was 20, he was 18. They both wanted desperately to move away from their parents and they got along so well that after four months of dating they got married. My whole life my mother has complained about my dad. She doesn't want to sleep with him, go out with him, kiss him, be near him. She will admit, like you, that he is an excellent father and husband. Maybe I'm a bit biased, but I don't think they make em like my dad anymore.
My mom's problem is herself. SHE isn't happy with her life before she got married. SHE isn't happy with who she married. SHE's not happy. With her it isn't what can I do to make others happy--it's what are you gonna do to make me happy and make me feel better about my past? If she would take one second to look at herself she would know that she doesn't need better life choices to make her feel better, she just needs to love herself.
It's not my dad's fault (or your husband's fault) that you feel you made the wrong choice.
It's not fair to your husband, your kids, or you to spend the rest of your life in guilt, despair, and unhappiness. You make a conscious decision to be unhappy. Pray that God will heal you of this. Let God show you what you need to do to feel better about you and your marriage. If you did leave your husband, would you feel any better about what happened or didn't happen 20 years ago? My mom is always looking for that one thing that is gonna make her smile again. What she doesn't realize is it's the one thing she has been blaming her failures on--my dad.
I don't know how you really feel deep down inside, but I know that God doesn't want you to suffer and the answer to your happiness may not be outside, but inside, your marriage.