Need help! it's not fair...

6 or 7 years ago I turned off child support on my ex-wife (by the court) because she was in and out of jail. After that neither of us had the children for 5 years. This year like in February she got the children back and in march I contacted her and started to see the children, she stated she didn't want child support, I could just help with what the children needed, and so I did, in the times I could (I live paycheck to paycheck). In September (6 months after), because a problem of religion (mine) she said she was going to take me for child support. Now they want me to pay 300+ dollars bi-weekly (800+ dollars a month) that I really can't afford. She gets help from the government, disability for one of my children and she quieted her job when she started living with her boyfriend (around February or March), I think this should be counted as her income because she purposely left her job to live off of her boyfriend's income. The case is going to court I really need legal representation to make sure she didn't lie about her income (if she really needed 800+ a month from me she should had done it 7 months ago when she got the kids back). I just want this case to be fair. Update: After having the children for a few hours in a MacDonald's, the were fitting on who wanted to lay their head on an arm rest in the car, the daughter ask for it first so I let her, my son started a tantrum I told him not to start with his tantrums, he's response to me was "you know why my mom yells at you on the phone because you can't do me like that" he went to his mom and told him I was mean to him and hurt his feelings, she called and she said she wants full custody she's going to have the power and I'm never going to see my children, my son is been having seizures for a while now, but she says is my fault because i hurt his feelings. I need help, I don't