Hi all,
Thanks so much for all your advice and suggestions!

I saw my GP yesterday and even though he could not properly answer for my why I didn't have a period in May (As my last period was April) and still fell pregnant in May he was helpful. He seemed to think that it is just one of those things that cannot be explained, like how some women still have a cycle or cycles in their first trimester!

Anyway he was able to explain to me in more detail the reasoning behind the radiographers assessment that I was only 15 weeks and not the 19 weeks we initially were told. According to all the measurements (There were about 7 different measurements taken ) the bub is at 15 weeks and the radiographer couldn't do too much that day because of that fact! So they have booked me in for my morphology scan in a months time (At 19 weeks) and I will know more then when they can do a more thorough scan and spend more time looking over bub!!

We are still keen to find out the baby's sex, and I am a little concerned with the placenta being low lying and so close to my cervix. They said that they will monitor that at the morphology scan and it it has not migrated enough away form my cervix as the uterus expands then they will have to check it again at around 32-36 weeks.

Anyway, I do feel better now after going to see my GP, and having him explain in more detail because it was a little bit of a shock to be told that you are 4 weeks behind what you thought you were, especially with such precise dates of last menstrual cycle!

So thanks again for your advice and concern, now I just have to re program my brain and set myself back 4 weeks!!

Tash