How long i need to be actively taking my bc to be protected..

Or to stop your period..?

I started my pill the beginning of august & i was due to start my period the 26th and ive been spotting since the 22nd.. i had sex during my fertile week, the week prior.. i dont want to jump to conclusions.. because it seems ever time i do and buy a test, i start my period just cant recall bc pills stopping my period so quickly accompanied by spotting.. except during my last pregnancy.