IUD (skyla)

I had sex a week ago and it was my first time ever having someone finish inside me. I have the Skyla IUD and have had it for almost year and a half. After I had unprotected sex I freaked out and took plan b 30/40 minutes after. A week had passed and I started having bleeding but not a lot. do you think I'm pregnant and this is implantion bleeding or just a period?