Why am I spotting on the day in supposed to have my period and it's been two days already. Pinkish/brownish discharge?

Don't know. The main reason for light periods is a change in hormone levels. Causes for what seems to be a light period can include: implantation bleeding in early pregnancy, thyroid problems, eating disorders, excessive exercise, initial periods for a girl, use of an intrauterine device, oral contraceptives & perimenopause.