Young, Married & Very unhappy,.... Pls help?

I am a 26 year old mother of 3 & 1 on the way. My husband is 8 y/older then me. I adpoted his 2 children and we have one together with one on the way. My husband is the the breadwinner and I do pretty good. When he gettes mad or depressed out his job he holds out his money on he is a plant manger and stress does weight heavy on him. But i am try of the abuse over these 6 years. My question : How do I get out of the relationship without breaking up or hurting any of my children, I love them all so dear. My children are the ones I really care about at this moment. They have been my love and joy for all the times mommy has been in pain, What do I do... I feel bad to want to break our union up.................?????