Periods

OK so normal my periods are heavy but recently my periods have been lighter and irregular. I've been on the same birth control for a year now. I would normally start 2 or 3 days into my sugar pills and then be done in like 5 days. I would cramp a little the week before but nothing major. Now it starts when ever it wants and it seems to have gotten lighter. My cramps are like demons are trying to escape.. and they're before and during now. Not sure what's going on. Anyone have any suggestions?