What Causes Abnormal Menstrual Discharge With Pain In Pelvic Region?

Hi I had 2 courses of anti biotics as I was displaying symptoms of PID, but all sexual health tests came as clear. In the last two months my periods have all but stopped. When blood does come out it s clotted, old, black dried up blood and a have stabbing pains in my pelvic area. I am very concerned but have to wait up to 8 mths for a gyni appointment. Any ideas what could be wrong with me?