One concern symptoms and conditions

WOW!! i havent had side of effects that bad thank god, but i do have one concern.. When i wasnt on pill my period would come normally and only last for three or four days.. Now my concern is that while on the pill my period will start on a thrusday and end a week later! while i start the pill back up that sunday.. it doesnt make sense.. im only on this period i had a medical problem and i was loosing a lot of blood but it's under control.. just except the long periods.. did any of u experience this bc idk what to do im on my 4th month and i got to go back in 2 or 3 months.. what should i do?? plz help