LW has some great suggestions for you. And what she says about the medical bills is very true. As long as you are making regular payments, there is nothing they can do about it.
I make a decent wage, but if I had to pay for child care, it would be very questionable if it would be worth it. Luckily (very luckily) my parents watch my daughter for me when she is not in school, so I don't have to pay for daycare and I know my daughter is with somebody I trust.
Are all three of your kids in daycare? I am assuming that only one or two of them are. Around here, the cheapest daycare is $20 a day. Latch key is $7 a day. Assuming that you have two kids in daycare and one in latchkey, that is $47 a day, or $235 per week. At 52 weeks, that is $12,220 (after tax unless you are using a Flexible spending account). Take in the cost of gas. For math, we will say that your car gets good mileage and you only use one gallon each way. That is $4.40 per day at the current costs, which ends up $1144 per year. Extra miles = extra car maintenance, which could easily add $1.00 (oil changes, tires, etc.) which is another $260 per year. Add the other costs such as: you probably eat out now and then for lunch, you probably take the kids to the doctor more because daycare kids get exposed to more germs, you have to wash more clothes because you need them for work, etc., and you can easily add another $500.
What does that add up to? $14,124 after tax. That means that you have to make (before tax) close to $20,000 per year just to cover the added expense. Say you make $32,000 per year (I have no idea- that's just an average wage for medium-high level office professionals in this area), that would mean that you are doing all this for $12,000 per year before taxes, which is roughly $8700 net, or $725 per month gross (that's $182 per week).
Chances are, you could find a way to make up that difference, or find a part time job (maybe doing latch key for local kids that you know) that could even out the gap.
Do you have any skills that you could turn into a home business? There are a lot of people who run fairly successful home businesses based on the need to stay home with their kids.