What Causes Delayed Menstrual Cycle After Abortion?

on 8 oct 2010 i got my abortion.after that 5 times menses come with irregular dates now this is 6th time and acording to my date 3 days over but menses has not come but i am feeling all my menses sympotoms.i am so much worried why menses is not coming.i am also feeling my belly and hips heavy.plz reply i am worried