Suggest Treatment For Irregular Menstrual Periods

hi doctor i am 22 years old unmarried
i am having very irregular periods
i am not having PCOD problem or thyroid problem
doctor prescribed me krimson 35 for 6 months
during the course every period is regular but this months my course have ended .
my problem is this month after stopping the tablet sep 2th i have the period and since then till now 22 days i am bleeding ... i am worried about this problem very much .please give me suggestion