the tests are accurate only 47% for 5 days before AF and teh percentage goes up.
re test in 3 days, and use FMU.

also it depends how many days Post Ovulation you are as to the amount of HCG in your system.

if you are only 8 DPO then you more than likely will have a negative result as it can take up to 12-16 days for implantation then 2-4 days for levels to rise to a level able to be read by a HPT.