Im 2 days late on my period and on the third i started noticing brown liquid took a pregnancy test and its negative , what could it be !?

What is it?: Brown liquid may be older blood being cleaned from uterus. It may be the start of your period. Can repeat pregnancy test in a week - if still no definitive menses. Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives, etc