What Causes Heavy Discharge In Periods?

Hi doctors, have experienced pain in my celvix there after now they is heavy discharge to the extent have to tharaly wash my vagina more than 3 times a day. my brief history am using contraceptive the injection one but the last injection i got was on 1st July 2010 and have not get my periods as yet. Please am getting worried now as its a second week now since its started need HELP!!!