I Had My Regular Period Last Time On 1 DEC,16

I had my regular period last time on 1 DEC,16 after in the same month again I have period on 15 DEC ,16 and it happened for the first time that I was having it twice in a month and till now no period..my gynaecologist given meprate for 3 days...2 tablet in one day and now only one tablet is left and still no period..how long should I wait after taking meprate and meet doc again?