Where can I get a free paternity test?

Q: I’m married to my wife for 13 years. When my last daughter was born, we decided on me getting a vasectomy. I had it done and didn’t produced any children. So last summer, she tells me she was pregnant(the baby was born in March), and I’m kinda surprised, but at the same time baffled, because we haven’t had any kids since 2002. I don’t know if the kid is mine because she told me she cheated, but the kid looks just like my son and myself. Please help me.

A: You can go to the drug store and buy a DNA test. But then there is a fee to get the results after you send it in. I don’t know how much it is. I don’t think you can get one for free unless you go on Maury.