Hi,
Some people use the IC cheapies fine, but a lot of people don't like them.
I think 8dpo is too early to test really as implantation only occurs on average 7-10dpo and even then it takes a couple of days to produce enough of the hormone to show on a test. It could be possible that you implanted early or perhaps ov'd earlier than you thought though so fx'd it's your bfp x