What are your ages?
Ages of the children?
How did you meet?
Will you be able to support yourself if you leave?
Is your only reason for not leaving is that you haven't figured out a "nice" way to do it?
How did your husband feel when you left?
Do you think your children would love him any less if you left?
Do you love him and want to work it out?
I asked about your ex because I wanted you to think about how he felt when you left. Have you thought about the possibility that maybe you shouldn't have gotten with this guy either? You have to decide if you love him enough to stay with him, or if you love yourself enough to leave. Studies have shown that couples that stay together for the sake of the children can cause more damage to the children than if they leave, especially when they are not affectionate towards one another and/or they argue. You deserve to be happy just as much as anyone else. If you cannot afford to leave then you have to try and talk to him about how you feel and let him know that you are unhappy. If he thinks you leaving would ruin his life, then he should be willing to compromise with you to make sure the both of you can be happy.
I welcome your thoughts, let me know if you want to talk more.