Late period with brown or pink discharge may be suggestive of implantation
bleeding in case of late conception.
test is less significant. Here, you need to repeat the pregnancy test after few days or undergo one blood test
for beta-hCG for confirmation.
Other reasons are pelvic infection
, stress, over wt, hormonal imbalance, late period itself etc. Kindly, consult with your doctor after undergoing the test.
Maintain genital hygiene. Good luck.