Thankyou for choosing HealthcareMagic.From what i could gather ,that you are on your thirteenth day of menses, which is of course prolonged or Menorrhagic.The causes of the same could be hormonal, oestrogen deficiency
, pertaining to pituitary-hypothalamus-ovarian axis, thickening of endometrium, fibroids/ adenomyosis
. Sometimes, a subtle miscarriage might present as prolonged periods
.It could even be due to some coagulation disorder/ bleeding disorder
. Hope you are not on any medication/ or herbs which is causing this. For this you may get your complete coagulation profile done. Consult a gynaec.Get well soon.