HOW EARLY IS TOO EARLY?!

Help a newbie out! What is the EARLIEST dpo you can get a bfp???? ๐Ÿ‘ถ๐Ÿฝ๐Ÿ‘ถ๐Ÿฝ๐Ÿ‘ถ๐Ÿฝ๐Ÿ•”