Here is a calculator you can plug in the dates of IVF and they give you all kinds of information about due dates and embryonic development.
If transferring a 5 day blastocyst on today's date:
I would be considered 2 weeks, 5 days pregnant.
A singleton pregnancy would be due: 2/1/2014.
Twin average gestation: 1/10/2014
Looks like my holidays will be spent relaxing on my big, pregnant butt! :)