Keen, my doc calculated my proper due date by minusing some days before transfer to take into account the FET and how old the embryos were at trasfer. My due date is actually the 2nd March (I was nearly right with the 4th!) and on all paperwork he has stated that the 26th May was the first day of my last AF (which is wrong, as it was on the 20th)
Being IVF and being a FET, it is all too confusing so I don't worry anymore. I won;t go full term anyway due to the twins so it's anybodies guess! Just another fun thing!

Hope everyone is well!