Ay, I get the confusion, sis! So if your last period was in December and it was only 2 days long, that's still counted as December, so one month na yun, and your next cycle would be expected around January pa. Pero honestly, kung ang period mo is normally 2-3 days lang, that's totally normal for some mamas, especially kapag first baby pa lang at nag-adjust pa ang body mo. Better mag-take ng pregnancy test if you're worried, or if your cycle becomes super irregular, best to ask your OB lang to be sure!