In my state you can file for modificaon if there is a change of 15%. If you are not able to get overtime, you may have to prove that in court. I have a co worker, he has three similar in ages.... his overtime is calculated into the CS payments. CS is about 45% of his gross. After taxes he is about in the same boat as you. I feel for him, but I see the other side too... kids cost, plain and simple. He doesn't begrudge his responsibility even though he doens't like it.