When you have your period it is 99% that you are not pregnant. If you are pregnant there is HCG in your system therefore even with a light period you can take the test and it would come up positive despite the bleeding. Vaginal bleeding during pregnancy will not affect the outcome of a pregnancy test. A pregnancy test will only look for HCG in your urine & will only turn positive when HCG has been found in your urine. Vaginal bleeding will not affect the result at all hun. However you should not be experiencing vaginal bleeding during early pregnancy. Light bleeding is common during the implantation bleeding process but not every pregnant woman will experience this. Brown spotting can also occur during pregnancy. A pregnancy test will only be negative when you're not pregnant or when you performed the test too early. A pregnancy test can usually performed 2-3 weeks after intercourse & the result will be accurate. However it is advisable you see your Doctor for a pregnancy blood test or if you suspect you're miscarrying, go straight to A&E for a thorough examination.