Did I Test Too Early?

on what i think was my 10 DPO i thought i saw a little pink when i wiped. i have been spotting for days (this is day 4). the flow has not increased at all. at times there is no blood when i wipe. the blood is mostly brownish but it has been light or bright red once or twice. i tested yesterday on what i believe is my 15 DPO and got BFN.

i think i may be pregnant b/c with DS the circumstances are very similar (spotting for a few days and never getting heavy) but i did not test until AF was about 5 days late b/c 2 years ago i didn't know about implantation bleeding so it took me a few days before i knew something was off with my cycle. however, now i know and it feels like 2 years ago.

it is very possible that i am off on my DPO b/c i don't chart. so is it possible that i tested early and should wait a little longer to test again?