Ay don't worry, yan talaga ang dating kapag may dating discrepancy sa LMP! Ang OB mo ay nag-base sa ultrasound measurements kasi yan ang mas accurate, ang dating from LMP ay pwedeng may error lalo na kung hindi mo exactly naaalala, like what happened sa'yo with Oct vs Sept confusion. A few of us mums went through this din, and what our docs explained is that early ultrasound (first trimester) is way more reliable than LMP calculations, so kung sabi ng scanner 12 weeks that time but doc says 13-14 now, it means baby grew normally in that one week gap, walang problema doon! Since your OB confirmed baby's healthy, good heartbeat, normal movements, at healthy na ang bleeding situation, I think okay ka na talaga, pero if you're still worried about the growth timeline, you can always ask your OB sa next visit to clarify exactly which week dating they're using going forward para peace of mind mo lang.