Possibly stupid question about missed periods

Usually I'm fairly regular, typically 24/25 day cycles (very fortunate with that) but this cycle I'm 3 days late (17 DPO) and no sign of AF arriving. Pregnancy tests are all negative.

So what happens if my period just doesn't arrive and is skipped? Should I start LH testing at some point and treat it as if I did have a period), do I just wait until AF arrives at some point in the future? I'm very confused 😭