Hi. Sorry your result wasn't a BFP. But yes, I think 8dpo is too early. While it seems like it can happen, I'd say wait until 10dpo or later. And probably for another blood test at least until AF is late. I know some women don't register on hpt for weeks after they are pg (or at least that's what I've been hearing on forums), and some not until they are 18dpo. It takes awhile for the hormone to get to the right level to be detected.
GL on getting your BFP.