For the past couple of years, once every 4-6 months I have been felt extreme pain in my lower abdomen. The muscle tightens up and the pain usually lasts for about 10-20 minutes and then goes away. Also, my vaginal discharge is sometimes brownish and other times it looks normal. I usually spot in between my menstrual cycles and experience slight pain when having sex. I have only had one sex partner and each symptom was occuring before i ever had sex. Does anyone have any ideas what this could be. Could it be PID?