Irregular period?

August 2 (period day): Only spotted once (no cramps or pain).
August 3-5 (period usually ends on the 5th): Had cramps on and off
(no stains).
August 6: Nothing at all. Thought it was a light period that passed.
August 7 (today): I'm bleeding so and so with stomachaches and cramps.
Is there any explanation for this? This is the first time this has happened.