What Causes Brown Discharge And Delayed Periods?

Hello, I am 9 days late with this month period but since yesterday night I had brown and sometimes reddish discharge but only when I wipe with tissue paper. i want to know the reason and what should I do? I did perg test when my period was late by 4 days and it came negative. I am 29 years old with 5.2 inches in height. usually I have my periods with a gap of 30-31 days. During my periods my mood swings but that is only for 1/2 days. But this time I am confused with the discharge and having no periods.