What Causes Irregular Periods?

i had my cesarian section 7 months ago (20Nov 2013). In last 7 months i had my period only once, assumed i was breastfeeding, and am continuing to do so. Three days ago, i started bleeding, and i thought its my period. But it does NOT seem so, as i feel am just bleeding fresh blood like water, no mucous, no clots, and when i stand up and walk, i wet the whole pad, and then i change it. When i lie down or sitting its ok. but again after sometime, when i stand up and walk, i feel blood flowing out, wetting the whole pad in one shot. Today is the third day, i feel discomfort and sometimes needle like pain in my lower abdomen, but its Not too much pain. But i do feel weak, although not dizzy.