PP period, maybe?

Kait🌱 • 26| Married| #1 due February| Parks&Rec
I'm currently 5 weeks pp. I started birth control almost a week ago and yesterday I got what seems to be my period. I'm exclusively pumping also. I guess my question is, is it an actual period, or the birth control? Should I call my doctor? I'm obviously a ftm lol. Any info would be great. Can't seem to find what I'm looking for online. Thanks!