When should i take a test , period or pregnancy ?

When you take a pregnancy test the test looks for the hcg pregnancy hormone in your urine. I doubt your testing too soon seeing as you missed your period. The light bleeding you experienced could be implantation bleeding which is a sign, but it's very uncommon. It's possible that your body just isn't producing enough of the hormone for the test to pick up. Try testing first thing in the morning, that's when you can get a more accurate result. If it's still negative, get a blood test done to confirm whether you are or aren't. Good luck.