With when Sun got pregnant, we also have to take into concideration how long before they came to the island was it when Jae & Sun were together.. If she was working on coming to America and leaving Jin.. The funeral for Jae & then getting on the plane in Sidney it would not add up anyway she would be further along I would think..

__________________
Please don't give up, Des. Because all we really need to survive is one person who truly loves us. And you have her. I will wait for
you. Always. I love you, Pen

DESMOND: I love you, Penny. I've always loved you. I'm so sorry. I love you!
PENNY: I love you too.
DESMOND: I don't know where I am, but--
PENNY: I'll find you, Des--
DESMOND: --I promise--
PENNY: --no matter what--
DESMOND: --I'll come back to you--
PENNY: --I won't give up--
BOTH: I promise. I love you.