Brown Discharge after bfp??? (TMI pic)

Lindsay • 32 yr old RN, married for 5 years. 🌈/🌈/WDR 10-23-17/TTC #2
Sorry I'm sure this has been asked - thousand times before. I just found out I'm pregnant after 2 prior chemical pregnancies, so if I carry to term this will be my first baby. According to Glow I'm almost 4 weeks, but I know I conceived around 2/10 or 2/11. My line is super dark this morning but I've also started having light brown discharge, like the kind I usually get before my period. No other symptoms really. Is this normal?? And at what point should I be worried and call my Dr.?