How many days until I can test for a positive pregnancy test

How many days after sex/ after ovulation window is over/ day 14 of cycle to test for a VFP ?? asking for help- I’m on day 20 of cycle, and period due in 8-10 days. When is the soonest I can test I don’t want to wait until the first day of my period. My boobs are extreammmmlyyyy sore.