Does Delay In Periods And Abdominal Pain Indicate Pregnancy?

I am 12 days late on my period, and my usual cycle is 28 days.
I have been feeling very tierd, and sick lately and suffering from slight lower abdominal pain. I have not take a pregancy test yet. I then today, started light bleeding which has got a little heavier, i think this may be my period starting today. Does this mean i still could be pregnant ?
Or does this mean I will now be in the all clear ?
I am just asking, as it is unusual for my period to be this late.