3 kids and a wife on a single salery seems rather much, especially in a nation like the US with very limited welfare services..
Like others I also wonder why you would have so many children without making sure your economy can support them and that you have back up savings incase things went sour..
But done is done I guess, so now it's all about cutting down on everything - so if possible move into a cheaper home, cut all the unnessesary expenses such as cable TV, car, internet sites, phone subscriptions etc etc and start paying off the debt that will surely come from getting into that situation ASAP even if thet means second or third job until your wife can work.. yeah it sucks, but 3 kids is a choice and it's a choice that means that they are your top priority now over everything else and a responsibility that you have chosen and should do all you can to live up to! You need to give them a good childhood and you need to make sure they get to go to college and can make it on their own ( or you will be stuck with them even longer ;) )
Good luck mate!