need my period to be early

I need my period to be a week earlier than usual as it falls at an inconvient time in 2 months... is there anything that could speed up my cycle? Would a GP be able to prescribe anything?
I am not on any form of birth control. 
I do have some birth control pills left that I stopped taking 3 months ago. 
However I don't want to start taking them again as I will have some break through bleeding that I don't want.