my period is lasting a lot longer than normal

Sydney

okay so i started my period last week and i also started birth control on the same day because that’s what the instructions said to do. my period has always been 7 days long since i started it 5 years ago. but this time i’ve been taking my birth control everyday and now i’m on my 10th day of being on my period and i’m still bleeding. is this a side affect of just starting birth control?? or should i go to the doctor? someone please help me!!