Excessive Bleeding on Birth Control?

I started the pill a little over three weeks ago and I'm on my first placebo week. I got my period 2 weeks after I started on birth control and its been going on for over a week, I know during the first few months your cycle can get really weird until your body gets used to it but its starting to feel excessive and everytime I think the period is going away it comes back. Anybody have any helpful info?