What Causes Dizziness,backache And Fatigue?

My period was due Friday and is set to end tomorrow, i am always regular and always have severe cramps and tender breasts two days prior to coming on. However this time nothing and my period has not come. I am experiencing extreme fatigue and get waves of nausea and dizzyness. I took a test today which came back negative. Today i also had backache and mild waves of cramp. I began to bleed when wiping but this happened onto twice then stopped! Please help I have no idea what s going on with me and whether I am pregnant or not. I m not on any birth control and have been trying to conceive for the past 9 months now.