What Causes Delay In Menstruation, Abdominal Pain And Brown Vaginal Discharge?

Hi. I need some advice. I had sex on the 20th of December,and I haven t had my period . So far I ve had pains,Dark Brown discharge, Light brown discharge with pain. Am I pregnant? If I am, how can I get a natural abortion? I know you can t excatly tell me, but I know you know how. Please tell me. My future depends on it. Regards