Spotting is blood that results when a fertilized egg nestles into your uterine lining. If you notice some light spotting on your underwear, the million-dollar question will start zinging through your head: Am I pregnant or is this the start of my period? Spotting is more likely to be a pinky-brown color. Menstrual bleeding, on the other hand, may start off light pink or brown, but it soon changes into crimson red. Spotting is usually super-light bleeding. Your period may start off light, but the flow gets stronger. Cramping that signals spotting is usually light and short-lived. Cramping that comes from your period is usually more intense and lasts longer. Every woman has her own pain threshold: You know your body best, so listen to it. If you notice clots in the bleeding, you can be pretty sure that this is your period. Spotting will not produce this mix of blood and tissue. Implantation bleeding lasts 1 to 3 days while your period lasts 4 to 7 days.