period on pill

kay • 20| UT
This may seem dumb but how come during the placebo week we get a period because I thought the pill made it so you weren't ovulating..so how is a period even posible? Also my doctor told me I would only get some sort of period on that week and it lasted the whole week on the sugar pills...I'm only on my second month do you think it won't be as bad as time goes on?