How common are they?

I’m at CD36, usually 30-32 max... I’ve never been late more than a day or two. Didn’t track ovulation, so truly have no idea how many dpo I could be.

Last faint positive I had was around 14dpo, so if I ovulated later or implanted later I’m likely too early to pick up.

Per LMP I’m 4 weeks 3 days out, and some apps say it’s common to get to 5 weeks before a positive. Is it?