Not everyone show a positive with a home pregnancy test. I suggest you go see your doctor and ask for a blood test to see if you are pregnant and if you are not then you would need to find out what else could be wrong.
I thought I had my period but when it didn't stop I went to the docs (after three weeks of bleeding) and found out I am pregnant.
I bled for 2 and a half months and it has finally stopped. I am 16 weeks now.
Lots of times bleeding could mean a possible miscarriage or a threatened miscarriage. Still, check with your doctor to make sure.