Help- Extremely Long Period

Alright ladies, I have been on my period for like 44 days now. I’ve had some light days and days with no bleeding. I’ve been to the doctor. They did an ultrasound, and everything appeared to be normal. Because of the prolonged bleeding, I experienced severe anemia which has been successfully treated. I am currently taking 3 BC pills a day in an attempt to make the bleeding stop. So my question for you all is have you ever experienced this or know anyone that has? What did they do to resolve the issue? Were they diagnosed with anything? My doctor recommended the nexplanon, what has been your experience with this form of BC? Also, I am 16, and I am NOT sexually active. I have been having a period since the age of 11, so in theory I think they should be semi regular by now. Unfortunately, they are very irregular. Sometimes I even go months without any signs of bleeding. Thank you!!