Wow!!!! You need to get lawyer. Who has the kids the majority of the time or do you all split 50/50? If the time spent is 50/50 then you will have to pay less.
Just out of curiousity have you ever figured out what you would have to pay? If my H were to divorce me, I would get around $800 for child support. Not that I want it to come to this, I am just keeping my options open just in case.