What Causes The Discharge Without Having Periods?

I was suppose to start my period the 22nd of May and I started having brown discharge only when I wipe on the 20th today is the 25tj and only thing I get is a reddish color when I wipe not enough to wear a pad or tampon it don t leak into the underwear . It s only there when I wipe I took a pregnacy test the 24th it took less then five seconds to show negative ? What is happening