My period is 6 days late and i have took 2 test and both have said negative.and tonight i just noticed a brownish/ red mucus blood! what does it mean?

That is older: blood mixed with other secretions. When blood is brown it is usually older blood from the uterus. You may be starting a late period. Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug >