You don't get your period (bright red, light, heavy, light) when you are pregnant. In early pregnancy you could have implantation bleeding around the time of your period (light pink/brown and spotting)
No your Period can be up and down and different cramps and heavy or light just because your period is light and not normal cramps does not mean you are pregnant. But if you start to feel sickness and your nipples are hard and pointy see a doctor to take a pregnancy test.
you'll want to contact your doctor immediately it could be as simple as you have your normal periods while pregnant or it could be a sign of a miscarriage either way talk to your doctor as soon as you can