Brown, heavy period for over a week?

Last week i went to the clinic to change my pill because my skin was bad. I started taking the pill the day i started my period like normall. I was on my period for about 3 days (which is usual for me) however, a couple of days after, i came back on. Its been unusually heavy, and a really dark brown. Im half way through my pack of pills for a month, and still on my period? So ive been on my period for about a week and a hallf! its strange because by the time i finish my pack again, i would be expecting my period again, but surely this wouldn't be right because it would only be a couple of weeks gaps between both periods? Im so confused. Is this normall??