7 Weeks PP -Period/BC Question? HELP!

I had my 6 week checkup last week with the doctor and he gave me some birth control to start on, one that won’t decrease my milk supply as I’m breastfeeding throughout the night and pumping during the day.

I’m on Day 5 if taking it and I started bleeding, like a period, a couple days ago & still am. Bright red, pretty heavy. I haven’t had any cramps or anything with it.

Is it likely my period starting or a side effect from being back on birth control?? 😭😭 Didn’t think I had to worry about my period due to BFing 🙄😑