C.O.
I've only had 3 periods since my baby was born December 2006. The first two were 6 1/2 weeks apart. The third was on time but I was on the pill by then.
It is possible that you are pregnant if you ovulated later in your cycle than usual. I have a friend who got pregnant on day 67 of her cycle, if you can believe that! She kept taking tests since she hadn't gotten a period and they kept coming back negative.
It is also possible, and more probable, that your body is just not quite on track yet. I would wait another week or so before taking another test if it doesn't start.