Birth control not strong enough??

Lion • Do not go gentle

A few months ago I tried to skip my period by starting a new pack of pills instead doing the withdrawal week, and I didn’t bleed for like half the week but then the period came anyway. So I am wondering if the pills weren’t enough to stop my period are they strong enough to prevent pregnancy? It seems like the hormones in my pill couldn’t overcome my natural hormones, so I’m concerned that it’s not strong enough during naturally fertile times too.