Why would my daughter bleed for almost a month nonstop ? Birth.cont.pills given 6 days still bleeding ??

She has been having this prob.for months but never for 3 weeks straight. Bleeds bad and has been given a pill to take for 7 days and still non-stop bleeding . Has taken birth control pills for 6 days now and still bleds. She is getting worried sick !1 She looks pale. Should she be worried?? Poor baby soaks towels !! She is not pregnant or had a miscarraige either. She is only 24 yrs old. I sure could use some prof. medical advice to give her...Serious answers only please. Should we take her back to Dr. or wait a few more days for birth. control pill to work ?