Thanks for the query.
You once undergo ultrasound
to find out the endometrial pattern and to rule out possibilities like poly cystic ovaries, endometriosis
and pelvic infection
profile was not done previously, go for it once.
If cause is found out by these investigations, you can get treated accordingly.
Dark appearance of the bleeding can be due to collected blood in the uterus during shedding of endometrium.
No need to worry about the color of the blood.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429