heavy periods!!!

I'm on seasonique birth control and have been on it for almost a year now (been on different pill brands before since I was 15, I'm now 22.) my periods have been lighter since I started taking the pill but are still really heavy, (on a bad day I'll go through a maxi pad every 20-60 minutes) any ideas as to what the problem might be? 
Note:I am speaking to my doctor about this and she is running test, just want some opinions