Women's Health Forum: I should know the answer to this one after going through all my science classes in college but want to make sure... Does getting a period, no matter how light it is, mean that you are NOT pregnant? For instance, if I got my period a week after I had sex, does that mean for certain that I am not pregnant? For some reason I am thinking that I can still be pregnant but cannot remember the logic behind it. Thanks for any help! Have you ever had a period while you were pregnant?