I'm not disagreeing with all those who declare that divorce is the way ahead, but I would like to make a couple of comments before you choose that route.
Divorce is not automatically a means to a happier life. It is in itself hugely upsetting, and once you are divorced, you are left on your own. No-one else to help with your life, or with the children; rather, you have the added difficulty of helping your children come to terms with Daddy not being around any more.
I know several women of my age who are still looking for someone to appreciate them and make them happy. Singledom isn't filled with hoardes of available men waiting to demonstrate that they would be better. It's filled with rats and love cheats, men who are married or gay but don't tell you, and so on. It's hard enough when you are single to meet nice men, it's even harder when you are older/have a couple of children to consider.
Whilst you are still married to this highly imperfect man, you at least have one thing. You are married. And he is the father of your children. This is something. Maybe a starting point. Once you are divorced from him, you do not have even that.
I once worked for a lady who was going through a divorce. He played some dirty tricks on her, met other women and it was all a bit unpleasant. However, all these tricks slowed the proceedings down, and with time, they started to see that in fact they were better off staying together and rubbing along civilly than completing the divorce. 20 years later, they are still together, the children are grown up, and they look back on a bumpy life together. I would actually say they are happy.
All the best with whatever you decide; I hope you find a happy way to proceed.