First off – go get another pregnancy test and test again. They sell pregnancy tests at the Dollar Store – and ALL pregnancy tests test for the same hormone.
Second off – yes, you could be pregnant. That light bleeding you had 5 days before your period was due could possibly be implantation bleeding, which is the bleeding you experience while the egg is making its home in the wall of your uterus.
Take a test now that you are past due on your period. Most of the time the tests are 99% accurate.
-Kim