What do you do when you feel like the world is against you?

I amm only in my mid twenties, am married with two children but I feel like I can never get a break. I work my tush off both at home and at work, yet when have applied for jobs get turned down. I treat my husband like a king yet I find out that he has cheated on me. My parents don't call, and when I do they don't want to talk. I feel like the only positive thing in my life is my kids I would do anything for them, I just want to give them a better life then I had, but I feel like a failure.