Congrats Melb Girl...

The dates from you last AF is not always correct unless you have a 28 day cycle.

You need to take into account cycle length... So if you Google 'Pregnancy Expected Due Date calculator' and go to the site (one or two down the list) it's called www. hpathy something... you can put in your LMP, Cycle Length and LP if you know it. It will tell you your EDD, when you concieved, and how many weeks you are!!!

Good Luck