What Causes Brown Vaginal Discharge And Upper Abdominal Pain?

I am 32, with as yet untreated PCOS, with both ovaries having many cysts (transvaginal ultrasound). Irregular periods maybe one or two a year. I am not sexually active, not on birth control pills or any other medication.

For five days I have had excruciating low back pain, with brown discharge (only on wiping), and dark brown spotting (very small amount). Pelvis feels full but not painful, and have started to get some upper abdominal pain. Do I need to see a GP or is this just a natural variant of PCOS?