Have a question about DPO and cycle length to next period.

Okay firstly I apologize if this is a silly question, but this question has been on my mind lately. So I understand your count of DPO days start promptly after ovulation. These are the days that we all count to judge when to test for pregnancy. I guess my question is how does DPO relate to you having to wait until the start of your period, missed period,  to test? I keep reading how it should be 12 DPO that is normal to initially test because that is when you would miss your period. So, what happens when your period is still like 2/3 days away and you are at 14DPO and still getting BFNs? Does that mean your chances are much lower even though you haven't missed a period? I'm just confused I guess about how this works. Any insight would be great. Also, if just being super slow this morning...please be gentle! 😂 I've had a rough week.