I have pcos & irregular periods and i lost weight. now my periods are heavier & more painful. why is that? is it normal

Changed periods: Congratulations on your weight loss! heavier cycles and more cramps during your cycles may indicate possible ovulation. Usually ovulatory cycles are associated with some cramping during the bleeding.

Period problems: It might be a good idea to monitor your basal body temperature charts. This can help you determine if you are ovulating, and can pinpoint what time in the cycle you are bleeding, ie is the bleeding a normal, but heavy period, or bleeding not related to dropping Progesterone 14 days after ovulation. You may have a polyp or fibroid which could complicate the periods as well.

Possibly normalizing: Irregular periods associated with pcos is likely associated with infrequent ovulation. With normalization of periods, females ovulate and can have "normal" menstrual symptoms. If this is your first period after a long time, you may have accumulated more than usual endometrial tissue which, during a period, would be shed. That could also cause more than expected bleeding.