Pregnancy or BC side effects?

Sydney

Okay ladies- I went to the gynecologist on Tuesday of this week to start on the pill. The last time I had sex was September 10th and I am supposed to start my period in 4 days. I saw brown discharge in my underwear yesterday and I don't know if that could be a side effect from starting the pill or if it is a sign of pregnancy. If anyone could help me out with what this is please do. Thank you!