Is it normal to have irregular periods after taking birth control pills?

Patient's question:

Patient Information: Female, 22 years old
Medical History (Onset time, main symptoms, etc.): I have always experienced a relatively small amount of menstrual blood flow, and on the first day of my period, my lower abdomen has been in pain for about 6 hours. Before my period starts, my left chest also hurts. This has been going on for 4 years. However, after taking a birth control pill at the end of October, my menstrual blood flow in November was very light, and my lower abdomen didn’t hurt anymore. This month, in December, my menstrual blood flow is even lighter—only on the second and third days, it’s equivalent to what it usually is on the fifth day. There were no warning signs before this period. A pregnancy test showed I’m not pregnant. I’m seeking help from all my friends—is this normal? Should I see a doctor and take medication to regulate it?
Past Treatment History and Allergies/Genealogy: None. It has always been normal before.

Doctor's answer:

This situation is likely caused by birth control pills leading to menstrual disorders. There is no need to worry; generally, the menstrual cycle can return to normal after stopping the pills for 2-3 months. Birth control pills should not be used more than three times within a year, and only once per month. Gynecological diseases are a common condition that can easily occur. During treatment, women need to pay attention to self-care, especially in terms of hygiene. It is recommended that patients avoid sexual activity during treatment and maintain good hygiene. Finally, we wish female patients a speedy recovery.