Does your period automatically sync to birth control once you start taking it?

Yes, but: Yes, but it may take a month or 2 or 3. It's not unusual in the first 1-3 months to have some bleeding between periods, even if you take the pill perfectly. If you miss pills, you're more likely to have irregular (or "breakthrough") bleeding. Write down the dates of your period, and ask your doctor if it doesn't correspond to the "placebo" or reminder pills.