it is possible, the same thing happened to my aunt after 7 years but she got lucky and was blessed with a little boy she has two daughters, she did not know she was prego she went to the dr office cause she thought she had the flu the dr came back and told her congrats shes prego my aunt and unck fliped he ran to the dr to have him self checked the dr told him that his vesectomy came back needless to say after my hansdsom nephew was born auntie tied her tubes. So you can have his checked to see if he still got dead sperm or if his vesectomy came back? but FYI those things do grow back from what the DR, told my aunt. so test or BT. to double check have him checked too and good luck hunn
You have adorable children. I don't know what to think, first a + then a - . Have you done any more tests? Were they both from the same box/brand? I'm intrigued!
Very possible that you are pregnant, Either wait a few days and test again or ask your doctor for a blood preg test and that way you will know for sure. Good luck and keep us posted. :)