It’s a bit confusing but that’s actually an outdated way of tracking ovulation, as you follicular phase (the time between the start of your period and the day you ovulate) can vary, whereas your luteal phase (from o day till the start of next period “or two week wait”) is always going to be the same amount of days. So yes in a perfect world the average 28 day cycle is about half and half (14 days FP and 14 days LP), but unfortunately for us the only true way of knowing the amount of time between o day and the start of your period is memorizing your body over time.
I thought I was O-ing the 14th day of every cycle too for a long time because I had a 28 day cycle and that’s what I’ve been told like you. But nothing was happening. And I would be late some cycles and early some and be totally confused. Then I started tracking ovulation, and counting the amount of days between confirmed ovulation day and whatever day I started my period that month. Turns out my LP was ALWAYS 15 days, but sometimes I Od on CD 12 and only had a 27 day cycle, while other times I Od anywhere up to cd18 and had a 33 day cycle.
Just keep tracking and learn your body, and it will all make sense. Best of luck to you, I’m hoping it’s just late implantation bleeding and not af! Keeping my finger crossed!