dates are taken from the first day of last period.
all pregnancies are different. My first pregnancy i didnt get sore breasts, morning sickness or any bad symptoms apart from tiredness.
it was all different with my second.
congratulations btw, i dont know if youd find this ivillage board of interest, everyone on there is pregnant and due same time as you.
http://messageboards.ivillage.co.uk/iv-ukpbmar 2010
of course, there are also loads of helpful people on AB too.