When do I test

Zoey
Alright so I had unprotected sex on the tenth I had bleeding on the 19th which I suspect might be implantion. Acording to Google you can get a positive 3 days after implantion so I should test on the 22? My period was supposed to be on the 20th but it hasn't arrived took a test today (not with first morning urine) and it was a bfn.