Ovulation/ Vent session

Natalie
This is probably a dumb question but I keep seeing people say they're testing "12 DPO and 8 DPO"... when should you test? I am going by when my next AF is due but is it better to go by when you ovulate? I took a Clear Blue Digital test this morning and got a BFN and my AF is due tomorrow. I took it apart because I read some of y'all were doing that and I could've sworn I saw a faint line on the test strip but felt crazy for thinking it so I just threw it away. Plus I had a pack of two and the first one was a blank screen and didn't work at all so I didn't have much faith in the one that I took that said negative. My husband and I have been "not trying but not preventing it" since we got married in July... I've tried to not let myself get too wrapped up in it because he is gone to training and we only see each other on the weekends so it'll be a super mega miracle if it happens right now anyways... but it's hard not to be disappointed when I keep getting BFNs every month. 😭😭 okay anyways that felt good to vent. 
Also I'm sorry I just realized I probably posted this in the wrong thread...I hadn't ever posted before..  I didn't take a pic of the test strip that came out of the digital test or I'd post it.. please don't be mad 😞