 [ Symptoms ] is my new girlfriend allergic to me i mean in a medical way [ Disease ] hi this bit below is from webmd so show her this it may help both of you sometimes you may notice that your menstrual blood becomes dark brown or almost black as you near the end of your period this is a normal colour change it happens when the blood is older and not being expelled from the body quickly temporary thick heavy flow is not necessarily cause for concern however regular heavy periods justify a trip to the doctor to check your blood counts many women become accustomed to heavy periods considering them to be normal over time though the excess monthly blood loss leads to anemia potentially causing weakness or fatigue if you ever feel something is not right with your period see your health care provider as for the pains could be just cramping has she had anything like this before do hope this helps you good luck