Put me a week ahead...which is IMPOSSIBLE. Hmm what to do? (XP - need advice!)

[Lashes85]

Well i've gained about 3 weeks :/
My LMP was 12th of Dec, i O'd on the 1st of Jan so 3 whole weeks after the first day of my last period (I was using OPKs)!! Yet when i went for my 12 weeks scan they only took 3 days off me. Meaning i was pregnant for 2 weeks and 4 days before i even ovulated lol. I must be having some big baby!! xx