Can't cope anymore

Hi. I'm feeling so alone, i haven't any friends apart from my wonderful partner but works away in the R.A.F.
I have 5 children from the ages of 11 to 5, I love them so much but the just take the mick out of me, they've had are hard time in the past 5years with the break up with their dad plus another bad relationship. The kids just don't listen to rules anymore I'm getting sick of the constant fighting, arguing and back chatting, it's getting to the point that the kids are making me ill, one imperticular child doesn't like me eating and I get called fat! Thinking of running away when their dad next has them? HELP!!