'Yasmin' for acne; period concerns

I've suffered with really bad acne recently, I've been through countless antibiotics and my next and only hope is Yasmin- the pill. 
This is new to me! I have serious questions about my period, I feel strongly that periods should come when they come and shouldn't be controlled. But my acne has got to that state where I'm going to have to deal with it. 
My period usually comes around the 14/15th and lasts a week maximum. Will this change at all?! I know I have that 7 day break, but that won't be around the 14th, will it? Meaning my cycle will be messed? 
Is there any extra info anyone can give me? Thank you xoxxoxo