You could be pregnant. In rare cases, a mans vasectomy can reverse itself, meaning that his tubes can grow back together. I have 2 friends in their 40's who have found out that they are pregnant several years after their spouses had vasectomies. He needs to go to his doctor to make sure he is still shooting blanks and you should go have a pregnancy test done.
OOOOO - we had number 3 five years ago, conceived 7 months after my husband's vasectomy. He had a second vasectomy at that time. Now, at age 44, I'm about 10 days late. I'm very regular and have no other pre-menapausal signs. I guess it's time for a blood test.