Brownish vag discharge

Marawii
Yesterday and during I was at work I notice there was small amount of brownish discharge and wasn't for long time. Besides I got headache before I found it and after few hours as well .and I still waiting the period which is after 2-3days . However I took a clear blue to check if I'm pregnant or not and I got negative result! Any one experienced same discharge before few days of period and negative result!