Brown vaginal discharge
/ spotting may be due to early implantation
bleeding/ sign of abortion or uterine cause. Do a blood test
for B-hcg & USG lower abdomen to confirm/ exclude conceptional product.
If both are positive, you should consult with your doctor for suggestive measures according to test reports. Dark nipple also signify changes in early week of pregnancy
Try to avoid stress, take healthy diet and maintain genital hygiene properly.
Be well & take care.