I have been having light brown discharge for the last five days . my period is due in a day or two. i am on birth control. could i be pregnant?

Possibly: Pregnancy is always a possibility. Purchase and perform a home pregnancy test. They usually become positive when you're about a week late. If it's negative, repeat it in 1 week and see your doctor.

Yes: Birth control pills aren't perfect, especially if you've take them late or missed pills, but other things can cause spotting-- polyps, fibroids, pregnancy.