Detecting DPO

Okay, so I've been reading a lot about testing around 9dpo. It seems like everyone is pretty confident when they ovulated. I'm not fully positive I ovulated when the app indicated I did, but my body has shown signs that confirms ovulation on those days. I have used another app that predicts I ovulated on the 22nd, but this app predicts the 25th. I guess I just don't know which day would be the best for testing with an ept. Im predicted to start my period on Jan 8. I'm very new to this if you can't tell! I'm trying to keep it under wraps or else I would ask my mom and sister about all this. God bless you, internet!! 😂