cryptic pregnancy?

had sex/took plan b in January.

haven’t had sex since.

my af has always been a steady 7 days a month for the last 9 years, and in March it dropped to 5 days randomly.

this month i’m going on 4 days late (i’ve never been late).

no stress at all that would be causing it (everything in my life seems so perfect lately, genuinely at peace, even this, I’d be ok pregnant or not pregnant).

urine tests still negative but haven’t blood tested.

what gives?