What Causes Pressure In Lower Abdomen And Stringy Vaginal Discharge?

Hi. I got my last depo shot in July 2010 and started on the bc pill in Sept 2010. Still haven't had a normal peroid since. For the past few days I've been expericeing alot of pressure in my lower abdomen to my vagina my thighs and buttocks. I've also been having brown stringy like dicharge from my vagina. In alot of pain. What is this and what can my Dr do for this. Its almost feels like I need to push. Help!