Can my husband decrease child support due to medical hardships?

Recently my husband and I were sent papers for child support. Apparently there is a possibility that he has another child that is 11 years old. We never knew about the child and now the mother is filing for child support. My husband went to take the DNA test and we are awaiting results. I am curious what our chances of lowering the payments if this is his kid? I am disabled due to a medical trauma in 2010 and I have very costly medications and health costs and we also have a disabled son. My husband and I have our own 4 children as it is. My husband is our sole financial provider. I am worried about this woman getting so much money from us when we never even knew this child existed and he is now old enough to say he wants nothing to do with the father because he has never known him! We barely make ends meet as it is and I don't know what we will do if we I cannot afford my injections for my health issues. I've read things about courts not usually cooperating with decreasing amounts, but I want other opinions! Also, we live 9 hours away from the county the mother and child live in, so it's an even bigger financial burden to fight this!