What Does Heavy Menstrual Flow With Lumps Suggest?

HI, I have been experiencing an extremely long period. For the past 8 weeks I have only not bleed for 5 days. The last 2.5 weeks have been more on the heavy side with what seems to be no end in sight. I am not cramping a lot, but have had a couple of days with headaches. I did pass a large lump about 3 weeks ago. It was the consistancy of several lump like shapes together forming the larger lump. I have never had anything like that before. The blood that I am passing is bright in color. Any idea of what might be wrong, or what I should do?