 [ Symptoms ] i have dark circles under eyes body aches and fatigue could it be addison disease [ Disease ] there can be many reasons to have a light menstrual period or spotting while on the pill it does not necessarily mean you are pregnant birth control pills taken properly of course are highly effective so your chance of an unintended pregnancy is not very high can it happen yes so if you are having any other signs of pregnancy a home pregnancy test or a visit to your gynecologist would be in something to consider