Motherhood is a major life transiton. Women who suffer anxiety or depressive disorders before becoming pregnant may be at greater risk for postpartum depression.
Postpartum depression: Baby blues, or more?- http://www.ivillage.com/postpartum-depression-baby-blues-or-more/6-n-137716?ice=iv:mb:msg:kp 
How did you realize that you were dealing with something more than the baby blues? Was there a moment when you knew that it was something more?