bleeding on active pill

I just started birth control for the first time on the 28 but i started my period on the 27 and my doctor gave me a plan b on that day as well. My period wasn’t supposed to start until the 29. It is usually 4 days and light on the last two but it’s almost been a week and been really heavy and doesn’t look like it is coming to an end. sometimes it does and i don’t bleed but then it just comes back. what does this mean? i’m on enskyce.