Why havent i got preqnat?? !! ?

So since october 2009 ive taken birth control?? And on march 2010 istopped 6 months later witch was in sep 2010 i started?? And then bout 4 months ago till this day ihavent taken any?? and ive been having sex almost everyday Is there a possibility i cant have children?? Someone please help im almost 20 in 8days i started birth control wen i was 18