How To Prepone Periods?

Hi.my periods time is this month 18th.my marriage is also on same day.I want get my periods early means at least on 12tn of this month.iam in confusion right now.I consulelted my doctor.she gave me one tablet I.e primolut n for 4 tablets in 8 days that means I should start from today.she said u will get it 12 the or 13 the.I don t want any postpone.I want prepone periods.because my marriage function is one week.in my home everybody is scolding.I don t know wt to do.give exact answer to my question.if I start taking premolut n tablet from today when will I get my prepone periods.will I get on this month 12 the.