Texas Child Support?

Hi everybody. I am a single parent of 2 children and I have finally filed child support on my ex, who has not helped me out financially for the past two years. Anybody have any experiences with Texas child support and how the back child support works? Also, I make a decent living at around 30k but I still struggle financially. My ex thinks that since I make a good living(by his non-employed standards), that he shouldn't have to pay as much. He claims that I never have money because I live an extravagant lifestyle. Guys, my mortgage(just bought my 1st home) is $600 and I have a $99 car payment. And my childcare bill per month is $790 for my two children. So if you add up just my mortgage, car, and childcare that adds up to roughly 80% of my monthly take home. The reason I am telling ya'll all of this is that he says the child support reviewers will make him pay less because I make more than him. I know this probably pure crap but it has me worried-any advice or experiences?