birthcontrol

i need some info on birthcontrol. i'm skipping the white/sugar pills to not have my period. i take them every 4 months to have but that's it. so before i take those white pills can i get pregnant? i don't take them the same time everyday. i prolly should take them in the evening bc on the weekends i wake up later. but im very paranoid. so while i'm on BC i don't ovulate so i can't get pregnant but if i take them a few hours difference will that really throw it off??