Help me figure out if I owe taxes?

Help! I'm trying to figure out if I am actually going to get a refund. I had twins in the year 2010, bringing my eligible children for the child tax credit to 5 - so $5,000 is my potential credit. My federal taxable income is $18,950, bringing my taxes owed to $2,011. I didn't pay any federal taxes this year, however, because we always end up at 0 liability anyway. So, every tax site that I go to says I am eligible for both the child tax credit and the additional child tax credit - somehow, all the calculations come up with an estimated refund of $3,700. I'm uming this is the combination of the $800 Making Work Pay credit as well as the rest of my $5,000 child tax credit. Is it possible to actually get a refund? It would be like the IRS to pay me for having kids. I'm confused. Of course, the IRS tax estimator says that I won't owe anything but I won't get anything either. Any pointers?