Suggest Remedy For Irregular Periods

I am 29 married. I have late periods and in January and February and then I get periods well in time in March but now in April and this month periods were due on 5th but I didn t get. By the end of last week my doctor prescribed primulat n for three times a day for five days. Now fifth day completed on this Friday but still I didn t get my periods. What to do? Before January my periods were quite normal.