Does the spotting happen every time, or has it just been this cycle? If it's just this cycle, then you may not have ovulated this time around; when I've had an anovulatory cycle, the following period always starts off with spotting. If it's every time, then not ovulating could still be the cause (along with many other things, I'm sure), but not ovulating make it impossible to get pregnant.
And I got pregnant with my daughter on the cycle after an anovulatory cycle.
at 5:40 PM on Aug. 19, 2009