What Causes Headaches, Dizziness And Lightheadedness?

I been feeling lightheaded and dizzy.having headaches on and off feeling very weak.nausae been cramping every since my last period on and on beginning april24.2011and ended on april30.2011.but my came a day early may23,2011 and still cramping bad wiyh inside abdominal pain and when i have sex i feel uncompable.sometimes my left and right and left side hurts.plus back pains.had my tubes tied on june24,2010.but i heard some can get pregnant in their tubes.