Longer periods on first time birth control?

Patient: I started taking birth control (Yaz) on the 21st of January, the doctor who prescribed it said to start it on the first day of my next period. It’s now the 2nd of February and I am still bleeding, usually it only lasts 4-6 days. So i’m kind of worried as this is day 13 of bleeding. Is that a normal reaction when starting the pill?