What Causes Delay In Periods,headache And Dizziness?

Hi there I am on the contraceptive pill and for the first time in 5 years I haven't got my period, also no cramps. I usually get it on the monday of the sugar pills at the latest and it is now Wednesday evening. I have been a bit dizzy since yesterday (Tuesday) afternoon. I have had headaches and fallen over three times in the last two weeks. Just feeling a bit strange. any idea why?