when to test?

martina • 22, one 4 year old boy, one 2 year old girl and expecting my third in july
when do u all think i should test? apparently 3 of my fertile tracker Calender's say i ovulated roughly the 18th or 19th... i swear the passed two days I've been experiencing implantation bleeding.. i never spot and I've been spotting dark over these two days. (8dpo)