I think I started testing about 7DPO with the so called early HPT's that can give you a accurate result form as early as 7dpo and kept getting BFN's (i think I did about 4 or 5 different tests from 7DPO to 14DPO - yes was a bit obsessed, lol) but at 15 DPO I finally got a very faint positive with 2 different brands.