What Causes Prolonged Bleeding?

Actually i would to consult the situation of my wife.She's been bleeding for almost 17days,last month she was delayed but after five days she got her menstruation,then after the menstruation for five days i think its gone.Then after another five days she got menstruation again.So we try to consult a doctor then she told us that it might be a miscarriage but instructed my wife to undergo of transvaginal.So she did that and the result says"The cervix is closed.Endocervical canal is intact.There no focal lesion seen.THe anteverted uterus is normal in size measuring 6.2 x 4.36 x 3.8 cms.Endotorium is 3.1mms thick there is no focal lesion.There is no evidence of intrauterinegestational sac of more than4-5 sonar weeks.There is no abnormal cul-de-sac fluid.Both ovaries are normal in size and appearance.the right ovary measures 3.01 x 2.23 cms while the left ovary measures 2.3 x 2.26 cms.No adnexal mass is demonstrated.

then impression:
Normal sized anteverted uterus , NOrmal ovaries......
Now we give the result to the doctor and told us that it was just a dysfunctional bleeding so she ask my wife to take some medicine i forgot the name of the medicine ill try to ask my wife later but as what she told me the doctor told her that it is to control or stop the bleeding.,then the doctor askd her to return after ten days to know the result after the medication.She is worryi8ng too much will you please give me your opinion with this.thanks