What Causes Symptoms Like Tiredness, Sleepy And Abdominal Cramps?

hello doc i am 24 years female iawant to know about this that i havbe acramps in my abdomen.feeling dizzines,tiredness,sleepy more than usually , my last periods is on 2nd jan2011 now today i am one day over due to my periods i have also done ahome pregnancy test that is negative what should i do? plz help me