I've had my period for 9 days. I'm on birth control and started my period 2 weeks earlier than I should have. Should I be concerned?

Periods. Periods can be affected by many things even birth control pills or medications that affect how birth control pills work. The main reason to be concerned is if you have been bleeding a lot which can cause anemia. If u have recently been on antibiotics these can alter how your pills work thus your cycle. If u missed a pill or don't take them as constistently as possible will affect your cycle too.