K.E.
It took a long time for my period to return after both my daughters were born - and even longer the second time. I did breastfeed them both for a full year though and just figured that had something to do with it. My period didn't return until several months after stopping nursing completely. However, several of my friends had their periods return just a few months after the birth - even though they were breastfeeding.
Could it be the birth control that you are using? Sometimes that could affect your body in ways you wouldn't expect - especially if it's a new kind you haven't used before.