Could i still be pregnant if i tested BFN at 12dpo???

ok i just got my bfp a couple of weeks ago at 15dpo i tested every single day untill then and i only have a 10 day luteal so i was actually 5 days late before i got mine. also i had blood test done a few days later and it was 84 however earlier that day i tested with 2 predictor tests that measure at 25 miu and they were completely negative, so used a different brand using same sample and bfp straight the way so it can happen