Always start my period on CD 28

Consistently, I start my period on CD 28. I’ve always been super regular, almost so the hour, and even with tracking the last 6ish months on here, I always spot/bleed on 11dpo. Does this mean my ovulation is happening at the same time each month or can it differ even though I’m starting my period on the same day each month?

I’m just starting to wonder because I’ve always thought I knew when I was ovulating because of being so regular... but am starting to wonder if I can ovulate on different cycle days and that’s why I haven’t gotten pregnant yet?