Being abused and alone can be very scary, so I do understand how you feel so all alone.
You have children and feel trapped, which makes matters even worse. But, those children can give you strength to do the right thing for yourself and for them. They do not deserve to live in an abusive household. Any guy who will hit a woman, will also take his frustrations and anger out on the children. It is just a matter of time before he begins abusing them. Also, I am pretty sure they see the way your husband treats you. They may not have witnessed their father hitting you, but they are living in that house and trust me, these kids are already suffering the consequences of their father's actions. They cannot possibly have a whole mother when she is being abused.
Leaving an abusive relationship is very hard, but you are going to have to do it sooner than later because the longer you stay, the more damage you and the children will endure and it will only get harder and harder for you to leave. But, in your heart, you already know that.
If I were you, I would be working on an exit plan. There are helplines and woman centers who can help you get emotionally ready to leave him. I would seek out help, in a heartbeat.
Maybe if your husband can get some help, voluntarily, he can learn how to control his anger. I don't know if he can manage his anger, or not. But, either way, you should seek out counseling yourself and ask him to join you. The counseling will do one of two things: help your marriage and get him to realize that communication, not hitting, is the way to a healthy relationship. OR, counseling will give you the knowledge in knowing you tried to save the marriage, but now you will have the strength to leave him.
You have family who will help you at first, especially if they know you are being abused. Wouldn't you like to be free of a man who hits you? You deserve better. Get help, please.